package org.opentrafficsim.road.gtu.lane.perception;
   
   import java.io.Serializable;
   import java.util.HashMap;
   import java.util.HashSet;
   import java.util.Iterator;
   import java.util.LinkedHashMap;
   import java.util.LinkedHashSet;
   import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.SortedSet;
  import java.util.TreeMap;
  import java.util.TreeSet;
  
  import org.djunits.value.vdouble.scalar.Length;
  import org.djunits.value.vdouble.scalar.Time;
  import org.djutils.exceptions.Throw;
  import org.opentrafficsim.core.gtu.GTUDirectionality;
  import org.opentrafficsim.core.gtu.GTUException;
  import org.opentrafficsim.core.gtu.GTUType;
  import org.opentrafficsim.core.gtu.RelativePosition;
  import org.opentrafficsim.core.network.LateralDirectionality;
  import org.opentrafficsim.core.network.Node;
  import org.opentrafficsim.core.network.route.Route;
  import org.opentrafficsim.core.perception.Historical;
  import org.opentrafficsim.core.perception.HistoricalValue;
  import org.opentrafficsim.core.perception.HistoryManager;
  import org.opentrafficsim.road.gtu.lane.LaneBasedGTU;
  import org.opentrafficsim.road.gtu.lane.perception.RollingLaneStructureRecord.RecordLink;
  import org.opentrafficsim.road.network.lane.CrossSectionLink;
  import org.opentrafficsim.road.network.lane.DirectedLanePosition;
  import org.opentrafficsim.road.network.lane.Lane;
  import org.opentrafficsim.road.network.lane.LaneDirection;
  import org.opentrafficsim.road.network.lane.object.LaneBasedObject;
  
  /**
   * This data structure can clearly indicate the lane structure ahead of us, e.g. in the following situation:
   * 
   * <pre>
   *     (---- a ----)(---- b ----)(---- c ----)(---- d ----)(---- e ----)(---- f ----)(---- g ----)  
   *                                             __________                             __________
   *                                            / _________ 1                          / _________ 2
   *                                           / /                                    / /
   *                                __________/ /             _______________________/ /
   *  1  ____________ ____________ /_ _ _ _ _ _/____________ /_ _ _ _ _ _ _ _ _ _ _ _ /      
   *  0 |_ _X_ _ _ _ |_ _ _ _ _ _ |_ _ _ _ _ _ |_ _ _ _ _ _ |_ _ _ _ _ _ |_ _ _ _ _ _ \____________
   * -1 |____________|_ _ _ _ _ _ |____________|____________|  __________|____________|____________| 3
   * -2              / __________/                           \ \  
   *        ________/ /                                       \ \___________  
   *      5 _________/                                         \____________  4
   * </pre>
   * 
   * When the GTU is looking ahead, it needs to know that when it continues to destination 3, it needs to shift one lane to the
   * right at some point, but <b>not</b> two lanes to the right in link b, and not later than at the end of link f. When it needs
   * to go to destination 1, it needs to shift to the left in link c. When it has to go to destination 2, it has to shift to the
   * left, but not earlier than at link e. At node [de], it is possible to leave the rightmost lane of link e, and go to
   * destination 4. The rightmost lane just splits into two lanes at the end of link d, and the GTU can either continue driving to
   * destination 3, turn right to destination 4. This means that the right lane of link d has <b>two</b> successor lanes.
   * <p>
   * In the data structures, lanes are numbered laterally. Suppose that the lane where vehicle X resides would be number 0.
   * Consistent with "left is positive" for angles, the lane right of X would have number -1, and entry 5 would have number -2.
   * <p>
   * In the data structure, this can be indicated as follows (N = next, P = previous, L = left, R = right, D = lane drop, . =
   * continued but not in this structure). The merge lane in b is considered "off limits" for the GTUs on the "main" lane -1; the
   * "main" lane 0 is considered off limits from the exit lanes on c, e, and f. Still, we need to maintain pointers to these
   * lanes, as we are interested in the GTUs potentially driving next to us, feeding into our lane, etc.
   * 
   * <pre>
   *       1                0               -1               -2
   *       
   *                       ROOT 
   *                   _____|_____      ___________      ___________            
   *                  |_-_|_._|_R_|----|_L_|_._|_-_|    |_-_|_._|_-_|  a           
   *                        |                |                |
   *                   _____V_____      _____V_____      _____V_____            
   *                  |_-_|_N_|_R_|----|_L_|_N_|_R_|&lt;---|_L_|_D_|_-_|  b           
   *                        |                |                 
   *  ___________      _____V_____      _____V_____                 
   * |_-_|_N_|_R_|&lt;---|_L_|_N_|_R_|----|_L_|_N_|_-_|                   c
   *       |                |                |                 
   *  _____V_____      _____V_____      _____V_____                 
   * |_-_|_._|_-_|    |_-_|_N_|_R_|----|_L_|_NN|_-_|                   d          
   *                        |                ||_______________ 
   *  ___________      _____V_____      _____V_____      _____V_____            
   * |_-_|_N_|_R_|&lt;---|_L_|_N_|_R_|----|_L_|_N_|_-_|    |_-_|_N_|_-_|  e          
   *       |                |                |                |
   *  _____V_____      _____V_____      _____V_____      _____V_____            
   * |_-_|_N_|_R_|&lt;---|_L_|_D_|_R_|----|_L_|_N_|_-_|    |_-_|_._|_-_|  f          
   *       |                                 |                 
   *  _____V_____                       _____V_____                             
   * |_-_|_._|_-_|                     |_-_|_._|_-_|                   g
   * </pre>
   * <p>
   * Copyright (c) 2013-2019 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved. <br>
   * BSD-style license. See <a href="http://opentrafficsim.org/docs/license.html">OpenTrafficSim License</a>.
   * </p>
   * $LastChangedDate: 2015-07-24 02:58:59 +0200 (Fri, 24 Jul 2015) $, @version $Revision: 1147 $, by $Author: averbraeck $,
   * initial version Feb 20, 2016 <br>
  * @author <a href="http://www.tbm.tudelft.nl/averbraeck">Alexander Verbraeck</a>
  */
 public class RollingLaneStructure implements LaneStructure, Serializable
 {
     /** */
     private static final long serialVersionUID = 20160400L;
 
     /** The lanes from which we observe the situation. */
     private final Historical<RollingLaneStructureRecord> root;
 
     /** Look ahead distance. */
     private Length lookAhead;
 
     /** Route the structure is based on. */
     private Route previousRoute;
 
     /** Lane structure records of the cross section. */
     private TreeMap<RelativeLane, RollingLaneStructureRecord> crossSectionRecords = new TreeMap<>();
 
     /** First lane structure records. */
     private TreeMap<RelativeLane, RollingLaneStructureRecord> firstRecords = new TreeMap<>();
 
     /** Lane structure records grouped per relative lane. */
     private Map<RelativeLane, Set<RollingLaneStructureRecord>> relativeLaneMap = new HashMap<>();
 
     /** Relative lanes storage per record, such that other records can be linked to the correct relative lane. */
     private Map<LaneStructureRecord, RelativeLane> relativeLanes = new HashMap<>();
 
     /** Set of lanes that can be ignored as they are beyond build bounds. */
     private final Set<Lane> ignoreSet = new HashSet<>();
 
     /** Upstream edges. */
     private final Set<RollingLaneStructureRecord> upstreamEdge = new LinkedHashSet<>();
 
     /** Downstream edges. */
     private final Set<RollingLaneStructureRecord> downstreamEdge = new LinkedHashSet<>();
 
     /** Downstream distance over which the structure is made. */
     private final Length down;
 
     /** Upstream distance over which the structure is made. */
     private final Length up;
 
     /** Downstream distance at splits (links not on route) included in the structure. */
     private final Length downSplit;
 
     /** Upstream distance at downstream merges (links not on route) included in the structure. */
     private final Length upMerge;
 
     /** GTU. */
     private final LaneBasedGTU containingGtu;
 
     /** the animation access. */
     @SuppressWarnings("checkstyle:visibilitymodifier")
     public AnimationAccess animationAccess = new AnimationAccess();
 
     /**
      * Constructor.
      * @param lookAhead Length; distance over which visual objects are included
      * @param down Length; downstream distance over which the structure is made
      * @param up Length; upstream distance over which the structure is made, should include a margin for reaction time
      * @param downSplit Length; downstream distance at splits (links not on route) included in the structure
      * @param upMerge Length; upstream distance at downstream merges (links not on route) included in the structure
      * @param gtu LaneBasedGTU; GTU
      */
     public RollingLaneStructure(final Length lookAhead, final Length down, final Length up, final Length downSplit,
             final Length upMerge, final LaneBasedGTU gtu)
     {
         HistoryManager historyManager = gtu.getSimulator().getReplication().getHistoryManager(gtu.getSimulator());
         this.root = new HistoricalValue<>(historyManager);
         this.lookAhead = lookAhead;
         this.down = down;
         this.up = up;
         this.downSplit = downSplit;
         this.upMerge = upMerge;
         this.containingGtu = gtu;
         // if (gtu.getId().equals("922"))
         // {
         // visualize(gtu);
         // }
     }
 
     /**
      * Updates the underlying structure shifting the root position to the input.
      * @param pos DirectedLanePosition; current position of the GTU
      * @param route Route; current route of the GTU
      * @param gtuType GTUType; GTU type
      * @throws GTUException on a problem while updating the structure
      */
     @Override
     public final void update(final DirectedLanePosition pos, final Route route, final GTUType gtuType) throws GTUException
     {
 
         /*
          * Implementation note: the LaneStructure was previously generated by AbstractLanePerception every time step. This
          * functionality has been moved to LaneStructure itself, in a manner that can update the LaneStructure. Start distances
          * of individual records are therefore made dynamic, calculated relative to a neighboring source record. For many time
          * steps this means that only these distances have to be updated. In other cases, the sources for start distances are
          * changed concerning the records that were involved in the previous time step. The LaneStructure now also maintains an
          * upstream and a downstream edge, i.e. set of records. These are moved forward as the GTU moves.
          */
 
         // fractional position
         Lane lane = pos.getLane();
         GTUDirectionality direction = pos.getGtuDirection();
         Length position = pos.getPosition();
         double fracPos = direction.isPlus() ? position.si / lane.getLength().si : 1.0 - position.si / lane.getLength().si;
 
         // TODO on complex networks, e.g. with sections connectors where lane changes are not possible, the update may fail
         if (this.previousRoute != route || this.root.get() == null)
         {
             // create new LaneStructure
             this.previousRoute = route;
 
             // clear
             this.upstreamEdge.clear();
             this.downstreamEdge.clear();
             this.crossSectionRecords.clear();
             this.relativeLanes.clear();
 
             // build cross-section
             RollingLaneStructureRecord newRoot = constructRecord(lane, direction, null, RecordLink.CROSS, RelativeLane.CURRENT);
             this.root.set(newRoot);
             this.crossSectionRecords.put(RelativeLane.CURRENT, newRoot);
             for (LateralDirectionality latDirection : new LateralDirectionality[] { LateralDirectionality.LEFT,
                     LateralDirectionality.RIGHT })
             {
                 RollingLaneStructureRecord current = newRoot;
                 RelativeLane relativeLane = RelativeLane.CURRENT;
                 Set<Lane> adjacentLanes =
                         current.getLane().accessibleAdjacentLanesPhysical(latDirection, gtuType, current.getDirection());
                 while (!adjacentLanes.isEmpty())
                 {
                     Throw.when(adjacentLanes.size() > 1, RuntimeException.class,
                             "Multiple adjacent lanes encountered during construction of lane map.");
                     relativeLane = latDirection.isLeft() ? relativeLane.getLeft() : relativeLane.getRight();
                     Lane adjacentLane = adjacentLanes.iterator().next();
                     RollingLaneStructureRecord adjacentRecord =
                             constructRecord(adjacentLane, direction, current, RecordLink.CROSS, relativeLane);
                     this.crossSectionRecords.put(relativeLane, adjacentRecord);
                     if (latDirection.isLeft())
                     {
                         if (adjacentLane
                                 .accessibleAdjacentLanesPhysical(LateralDirectionality.RIGHT, gtuType, current.getDirection())
                                 .contains(current.getLane()))
                         {
                             adjacentRecord.setRight(current, gtuType);
                         }
                         current.setLeft(adjacentRecord, gtuType);
                     }
                     else
                     {
                         if (adjacentLane
                                 .accessibleAdjacentLanesPhysical(LateralDirectionality.LEFT, gtuType, current.getDirection())
                                 .contains(current.getLane()))
                         {
                             adjacentRecord.setLeft(current, gtuType);
                         }
                         current.setRight(adjacentRecord, gtuType);
                     }
                     current = adjacentRecord;
                     adjacentLanes =
                             current.getLane().accessibleAdjacentLanesPhysical(latDirection, gtuType, current.getDirection());
                 }
             }
             this.upstreamEdge.addAll(this.crossSectionRecords.values());
             this.downstreamEdge.addAll(this.crossSectionRecords.values());
             this.firstRecords.putAll(this.crossSectionRecords);
 
             // set the start distances so the upstream expand can work
             newRoot.updateStartDistance(fracPos, this);
 
             // expand upstream edge
             expandUpstreamEdge(gtuType, fracPos);
 
             // derive first records
             deriveFirstRecords();
         }
         else
         {
 
             // update LaneStructure
             RollingLaneStructureRecord newRoot = this.root.get();
             if (!lane.equals(newRoot.getLane()))
             {
 
                 // find the root, and possible lateral shift if changed lane
                 newRoot = null;
                 RelativeLane lateralMove = null;
                 double closest = Double.POSITIVE_INFINITY;
                 for (RelativeLane relativeLane : this.relativeLaneMap.keySet())
                 {
                     for (RollingLaneStructureRecord record : this.relativeLaneMap.get(relativeLane))
                     {
                         if (record.getLane().equals(lane) && record.getStartDistance().si < closest
                                 && record.getStartDistance().si + record.getLength().si > 0.0)
                         {
                             newRoot = record;
                             lateralMove = relativeLane;
                             // multiple records may be present for the current lane due to a loop
                             closest = record.getStartDistance().si;
                         }
                     }
                 }
                 // newRoot.getPrev().contains(newRoot.getStartDistanceSource())
                 this.root.set(newRoot);
 
                 // update start distance sources
                 updateStartDistanceSources();
 
                 // shift if changed lane
                 if (!lateralMove.isCurrent())
                 {
                     RelativeLane delta =
                             new RelativeLane(lateralMove.getLateralDirectionality().flip(), lateralMove.getNumLanes());
 
                     TreeMap<RelativeLane, Set<RollingLaneStructureRecord>> newRelativeLaneMap = new TreeMap<>();
                     for (RelativeLane relativeLane : this.relativeLaneMap.keySet())
                     {
                         RelativeLane newRelativeLane = relativeLane.add(delta);
                         newRelativeLaneMap.put(newRelativeLane, this.relativeLaneMap.get(relativeLane));
                     }
                     this.relativeLaneMap = newRelativeLaneMap;
 
                     Map<LaneStructureRecord, RelativeLane> newRelativeLanes = new HashMap<>();
                     for (LaneStructureRecord record : this.relativeLanes.keySet())
                     {
                         newRelativeLanes.put(record, this.relativeLanes.get(record).add(delta));
                     }
                     this.relativeLanes = newRelativeLanes;
                 }
 
                 this.crossSectionRecords.clear();
                 this.crossSectionRecords.put(RelativeLane.CURRENT, newRoot);
                 for (LateralDirectionality latDirection : new LateralDirectionality[] { LateralDirectionality.LEFT,
                         LateralDirectionality.RIGHT })
                 {
                     RollingLaneStructureRecord record = newRoot;
                     RollingLaneStructureRecord next = newRoot;
                     RelativeLane delta = new RelativeLane(latDirection, 1);
                     RelativeLane relLane = RelativeLane.CURRENT;
                     while (next != null)
                     {
                         next = latDirection.isLeft() ? record.getLeft() : record.getRight();
                         if (next != null)
                         {
                             next.changeStartDistanceSource(record, RecordLink.CROSS);
                             relLane = relLane.add(delta);
                             this.crossSectionRecords.put(relLane, next);
                             record = next;
                         }
                     }
                 }
 
             }
             newRoot.updateStartDistance(fracPos, this);
 
             // update upstream edges
             retreatUpstreamEdge();
 
             // derive first records
             deriveFirstRecords();
 
         }
 
         // update downstream edges
         expandDownstreamEdge(gtuType, fracPos, route);
 
     }
 
     /**
      * Derives the first downstream records so the extended cross-section can be returned.
      */
     private void deriveFirstRecords()
     {
         this.firstRecords.clear();
         this.firstRecords.putAll(this.crossSectionRecords);
         for (RelativeLane lane : this.relativeLaneMap.keySet())
         {
             getFirstRecord(lane); // store non-null values internally
         }
     }
 
     /**
      * Upstream algorithm from the new source, where records along the way are assigned a new start distance source. These
      * records were downstream in the previous time step, but are now upstream. Hence, their start distance source should now
      * become their downstream record. This algorithm acts like an upstream tree, where each branch is stopped if there are no
      * upstream records, or the upstream records already have their downstream record as source (i.e. the record was already
      * upstream in the previous time step).
      */
     private void updateStartDistanceSources()
     {
 
         // initial cross section
         Set<RollingLaneStructureRecord> set = new HashSet<>();
         RollingLaneStructureRecord rootRecord = this.root.get();
         set.add(rootRecord);
         rootRecord.changeStartDistanceSource(null, RecordLink.CROSS);
         RollingLaneStructureRecord prev = rootRecord;
         RollingLaneStructureRecord next = prev.getLeft();
         while (next != null)
         {
             set.add(next);
             next.changeStartDistanceSource(prev, RecordLink.CROSS);
             prev = next;
             next = next.getLeft();
         }
         prev = rootRecord;
         next = prev.getRight();
         while (next != null)
         {
             set.add(next);
             next.changeStartDistanceSource(prev, RecordLink.CROSS);
             prev = next;
             next = next.getRight();
         }
         // tree algorithm (branches flattened to a single set)
         while (!set.isEmpty())
         {
             // lateral
             Set<RollingLaneStructureRecord> newSet = new HashSet<>();
             for (RollingLaneStructureRecord record : set)
             {
                 for (LateralDirectionality latDirection : new LateralDirectionality[] { LateralDirectionality.LEFT,
                         LateralDirectionality.RIGHT })
                 {
                     prev = record;
                     next = latDirection.isLeft() ? record.getLeft() : record.getRight();
                     while (next != null && !set.contains(next))
                     {
                         next.changeStartDistanceSource(prev, RecordLink.LATERAL_END);
                         removeDownstream(next, latDirection.flip()); // split not taken can be thrown away
                         newSet.add(next);
                         prev = next;
                         next = latDirection.isLeft() ? next.getLeft() : next.getRight();
                     }
                 }
             }
             set.addAll(newSet);
 
             // longitudinal
             newSet.clear();
             for (RollingLaneStructureRecord record : set)
             {
                 for (RollingLaneStructureRecord prevRecord : record.getPrev())
                 {
                     Iterator<RollingLaneStructureRecord> it = prevRecord.getNext().iterator();
                     while (it.hasNext())
                     {
                         RollingLaneStructureRecord otherDown = it.next();
                         if (!otherDown.getLane().getParentLink().equals(record.getLane().getParentLink()))
                         {
                             // split not taken can be thrown away
                             otherDown.changeStartDistanceSource(null, null);
                             // this can throw away records that are laterally connected as they later merge... ??
                             removeDownstream(otherDown, LateralDirectionality.NONE);
                             removeRecord(otherDown);
                             it.remove();
                         }
                     }
                     LaneStructureRecord source = prevRecord.getStartDistanceSource();
                     if (source == null || (source != null && !source.equals(record)))
                     {
                         prevRecord.changeStartDistanceSource(record, RecordLink.UP);
                         newSet.add(prevRecord);
                     }
                 }
             }
 
             // next loop
             set = newSet;
         }
     }
 
     /**
      * Removes all records downstream of the given record from underlying data structures.
      * @param record RollingLaneStructureRecord; record, downstream of which to remove all records
      * @param lat LateralDirectionality; records with an adjacent record at this side are not deleted
      */
     private void removeDownstream(final RollingLaneStructureRecord record, final LateralDirectionality lat)
     {
         for (RollingLaneStructureRecord next : record.getNext())
         {
             RollingLaneStructureRecord adj = lat.isLeft() ? next.getLeft() : lat.isRight() ? next.getRight() : null;
             if (adj == null)
             {
                 next.changeStartDistanceSource(null, null);
                 removeDownstream(next, lat);
                 removeRecord(next);
             }
         }
         record.clearNextList();
     }
 
     /**
      * Removes the record from underlying data structures.
      * @param record RollingLaneStructureRecord; record to remove
      */
     private void removeRecord(final RollingLaneStructureRecord record)
     {
         RelativeLane lane = this.relativeLanes.get(record);
         if (lane != null)
         {
             this.relativeLanes.remove(record);
         }
         record.changeStartDistanceSource(null, null);
 
     }
 
     /**
      * On a new build, this method is used to create the upstream map.
      * @param gtuType GTUType; GTU type
      * @param fractionalPosition double; fractional position on reference link
      * @throws GTUException on exception
      */
     private void expandUpstreamEdge(final GTUType gtuType, final double fractionalPosition) throws GTUException
     {
         this.ignoreSet.clear();
         for (LaneStructureRecord record : this.upstreamEdge)
         {
             this.ignoreSet.add(record.getLane());
         }
         Set<RollingLaneStructureRecord> nextSet = new LinkedHashSet<>();
         boolean expand = true;
         while (expand)
         {
             expand = false;
 
             // longitudinal
             Iterator<RollingLaneStructureRecord> iterator = this.upstreamEdge.iterator();
             Set<RollingLaneStructureRecord> modifiedEdge = new LinkedHashSet<>(this.upstreamEdge);
             while (iterator.hasNext())
             {
                 RollingLaneStructureRecord prev = iterator.next();
                 Map<Lane, GTUDirectionality> nexts = prev.getLane().upstreamLanes(prev.getDirection(), gtuType);
                 if (prev.getStartDistance().si < this.up.si)
                 {
                     // upstream search ends on this lane
                     prev.setCutOffStart(this.up.minus(prev.getStartDistance()));
                     for (Lane prevLane : nexts.keySet())
                     {
                         this.ignoreSet.add(prevLane); // exclude in lateral search
                     }
                 }
                 else
                 {
                     // upstream search goes further upstream
                     prev.clearCutOffStart();
                     iterator.remove();
                     if (!nexts.isEmpty())
                     {
                         for (Lane prevLane : nexts.keySet())
                         {
                             RelativeLane relativeLane = this.relativeLanes.get(prev);
                             RollingLaneStructureRecord next =
                                     constructRecord(prevLane, nexts.get(prevLane), prev, RecordLink.UP, relativeLane);
                             this.ignoreSet.add(prevLane);
                             next.updateStartDistance(fractionalPosition, this);
                             connectLaterally(next, gtuType, modifiedEdge);
                             next.addNext(prev);
                             prev.addPrev(next);
                             nextSet.add(next);
                             modifiedEdge.add(next);
                         }
                     }
                 }
             }
             this.upstreamEdge.addAll(nextSet);
             expand |= !nextSet.isEmpty();
             nextSet.clear();
 
             // lateral
             Set<RollingLaneStructureRecord> lateralSet =
                     expandLateral(this.upstreamEdge, RecordLink.LATERAL_END, gtuType, fractionalPosition);
             nextSet.addAll(lateralSet);
 
             // next iteration
             this.upstreamEdge.addAll(nextSet);
             expand |= !nextSet.isEmpty();
             nextSet.clear();
         }
     }
 
     /**
      * Helper method for upstream and downstream expansion. This method returns all lanes that can be laterally found from the
      * input set.
      * @param edge Set&lt;RollingLaneStructureRecord&gt;; input set
      * @param recordLink RecordLink; link to add between lateral records, depends on upstream or downstream search
      * @param gtuType GTUType; GTU type
      * @param fractionalPosition double; fractional position on reference link
      * @return Set&lt;LaneStructureRecord&gt;; output set with all laterally found lanes
      */
     private Set<RollingLaneStructureRecord> expandLateral(final Set<RollingLaneStructureRecord> edge,
             final RecordLink recordLink, final GTUType gtuType, final double fractionalPosition)
     {
         Set<RollingLaneStructureRecord> nextSet = new LinkedHashSet<>();
         Set<Lane> laneSet = new HashSet<>(); // set to check that an adjacent lane is not another lane already in the set
         for (LaneStructureRecord record : edge)
         {
             laneSet.add(record.getLane());
         }
         Iterator<RollingLaneStructureRecord> iterator = edge.iterator();
         while (iterator.hasNext())
         {
             RollingLaneStructureRecord record = iterator.next();
             for (LateralDirectionality latDirection : new LateralDirectionality[] { LateralDirectionality.LEFT,
                     LateralDirectionality.RIGHT })
             {
                 RelativeLane relativeLane = this.relativeLanes.get(record);
                 RollingLaneStructureRecord prev = record;
                 Set<Lane> adjacentLanes =
                         prev.getLane().accessibleAdjacentLanesPhysical(latDirection, gtuType, prev.getDirection());
                 while (!adjacentLanes.isEmpty())
                 {
                     Throw.when(adjacentLanes.size() > 1, RuntimeException.class,
                             "Multiple adjacent lanes encountered during construction of lane map.");
                     relativeLane = latDirection.isLeft() ? relativeLane.getLeft() : relativeLane.getRight();
                     Lane nextLane = adjacentLanes.iterator().next();
                     if (!laneSet.contains(nextLane) && !this.ignoreSet.contains(nextLane))
                     {
                         RollingLaneStructureRecord next =
                                 constructRecord(nextLane, record.getDirection(), prev, recordLink, relativeLane);
                         this.ignoreSet.add(nextLane);
                         next.updateStartDistance(fractionalPosition, this);
                         nextSet.add(next);
                         laneSet.add(nextLane);
                         if (latDirection.isLeft())
                         {
                             prev.setLeft(next, gtuType);
                             if (nextLane
                                     .accessibleAdjacentLanesPhysical(LateralDirectionality.RIGHT, gtuType, prev.getDirection())
                                     .contains(prev.getLane()))
                             {
                                 next.setRight(prev, gtuType);
                             }
                             for (RollingLaneStructureRecord edgeRecord : edge)
                             {
                                 if (!edgeRecord.equals(prev)
                                         && edgeRecord.getLane().getParentLink().equals(next.getLane().getParentLink()))
                                 {
                                     for (Lane adjLane : edgeRecord.getLane().accessibleAdjacentLanesPhysical(
                                             LateralDirectionality.RIGHT, gtuType, edgeRecord.getDirection()))
                                     {
                                         if (adjLane.equals(next.getLane()))
                                         {
                                             edgeRecord.setRight(next, gtuType);
                                             next.setLeft(edgeRecord, gtuType);
                                         }
                                     }
                                 }
                             }
                         }
                         else
                         {
                             prev.setRight(next, gtuType);
                             if (nextLane
                                     .accessibleAdjacentLanesPhysical(LateralDirectionality.LEFT, gtuType, prev.getDirection())
                                     .contains(prev.getLane()))
                             {
                                 next.setLeft(prev, gtuType);
                             }
                             for (RollingLaneStructureRecord edgeRecord : edge)
                             {
                                 if (!edgeRecord.equals(prev)
                                         && edgeRecord.getLane().getParentLink().equals(next.getLane().getParentLink()))
                                 {
                                     for (Lane adjLane : edgeRecord.getLane().accessibleAdjacentLanesPhysical(
                                             LateralDirectionality.LEFT, gtuType, edgeRecord.getDirection()))
                                     {
                                         if (adjLane.equals(next.getLane()))
                                         {
                                             edgeRecord.setLeft(next, gtuType);
                                             next.setRight(edgeRecord, gtuType);
                                         }
                                     }
                                 }
                             }
                         }
                         prev = next;
                         adjacentLanes =
                                 prev.getLane().accessibleAdjacentLanesPhysical(latDirection, gtuType, prev.getDirection());
                     }
                     else
                     {
                         break;
                     }
                 }
             }
         }
         return nextSet;
     }
 
     /**
      * This method makes sure that not all history is maintained forever, and the upstream edge moves with the GTU.
      * @throws GTUException on exception
      */
     private void retreatUpstreamEdge() throws GTUException
     {
         boolean moved = true;
         Set<RollingLaneStructureRecord> nexts = new LinkedHashSet<>();
         while (moved)
         {
             moved = false;
             nexts.clear();
             Iterator<RollingLaneStructureRecord> iterator = this.upstreamEdge.iterator();
             while (iterator.hasNext())
             {
                 RollingLaneStructureRecord prev = iterator.next();
                 // nexts may contain 'prev' as two lanes are removed from the upstream edge that merge in to 1 downstream lane
                 if (!nexts.contains(prev) && prev.getStartDistance().si + prev.getLane().getLength().si < this.up.si)
                 {
                     for (RollingLaneStructureRecord next : prev.getNext())
                     {
                         next.clearPrevList();
                         next.setCutOffStart(this.up.minus(next.getStartDistance()));
                         moved = true;
                         nexts.add(next);
                         RollingLaneStructureRecord lat = next.getLeft();
                         while (lat != null && lat.getPrev().isEmpty())
                         {
                             nexts.add(lat);
                             lat = lat.getLeft();
                         }
                         lat = next.getRight();
                         while (lat != null && lat.getPrev().isEmpty())
                         {
                             nexts.add(lat);
                             lat = lat.getRight();
                         }
                     }
                     prev.clearNextList();
                     removeRecord(prev);
                     iterator.remove();
                 }
                 else
                 {
                     Length cutOff = this.up.minus(prev.getStartDistance());
                     if (cutOff.si > 0)
                     {
                         prev.setCutOffStart(cutOff);
                     }
                 }
             }
             this.upstreamEdge.addAll(nexts);
 
             // check adjacent lanes
             for (RollingLaneStructureRecord record : nexts)
             {
                 RollingLaneStructureRecord prev = record;
                 for (LateralDirectionality latDirection : new LateralDirectionality[] { LateralDirectionality.LEFT,
                         LateralDirectionality.RIGHT })
                 {
                     while (prev != null)
                     {
                         RollingLaneStructureRecord next = latDirection.isLeft() ? prev.getLeft() : prev.getRight();
                         if (next != null && !this.upstreamEdge.contains(next))
                         {
                             moved |= findUpstreamEdge(next);
                         }
                         prev = next;
                     }
                 }
             }
         }
     }
 
     /**
      * Recursive method to find downstream record(s) on the upstream edge, as the edge was moved downstream and a laterally
      * connected lane was not yet in the upstream edge. All edge records are added to the edge set.
      * @param record RollingLaneStructureRecord; newly found adjacent record after moving the upstream edge downstream
      * @return boolean; whether a record was added to the edge, note that no record is added of the record is fully downstream
      *         of the upstream view distance
      * @throws GTUException on exception
      */
     private boolean findUpstreamEdge(final RollingLaneStructureRecord record) throws GTUException
     {
         Length cutOff = this.up.minus(record.getStartDistance());
         boolean moved = false;
         if (cutOff.gt0())
         {
             if (cutOff.lt(record.getLane().getLength()))
             {
                 record.clearPrevList();
                 record.setCutOffStart(cutOff);
                 this.upstreamEdge.add(record);
                 moved = true;
             }
             else
             {
                 if (this.relativeLanes.containsKey(record))
                 {
                     // could have been removed from upstream already
                     removeRecord(record);
                 }
                 for (RollingLaneStructureRecord next : record.getNext())
                 {
                     moved |= findUpstreamEdge(next);
                 }
             }
         }
         return moved;
     }
 
     /**
      * Main downstream search for the map. Can be used at initial build and to update.
      * @param gtuType GTUType; GTU type
      * @param fractionalPosition double; fractional position on reference link
      * @param route Route; route of the GTU
      * @throws GTUException on exception
      */
     private void expandDownstreamEdge(final GTUType gtuType, final double fractionalPosition, final Route route)
             throws GTUException
     {
         this.ignoreSet.clear();
         for (LaneStructureRecord record : this.downstreamEdge)
         {
             this.ignoreSet.add(record.getLane());
         }
         Set<RollingLaneStructureRecord> nextSet = new LinkedHashSet<>();
         Set<RollingLaneStructureRecord> splitSet = new LinkedHashSet<>();
         boolean expand = true;
         while (expand)
         {
             expand = false;
 
             // longitudinal
             Iterator<RollingLaneStructureRecord> iterator = this.downstreamEdge.iterator();
             Set<RollingLaneStructureRecord> modifiedEdge = new LinkedHashSet<>(this.downstreamEdge);
             while (iterator.hasNext())
             {
                 RollingLaneStructureRecord record = iterator.next();
                 Map<Lane, GTUDirectionality> nexts = record.getLane().downstreamLanes(record.getDirection(), gtuType);
                 if (record.getStartDistance().si + record.getLane().getLength().si > this.down.si)
                 {
                     // downstream search ends on this lane
                     record.setCutOffEnd(this.down.minus(record.getStartDistance()));
                     for (Lane nextLane : nexts.keySet())
                     {
                         this.ignoreSet.add(nextLane); // exclude in lateral search
                     }
                 }
                 else
                 {
                     // downstream search goes further downstream
 
                     // in case there are multiple lanes on the same link after a lane split, we need to choose one
                     LaneDirection nextLaneDirection =
                             new LaneDirection(record.getLane(), record.getDirection()).getNextLaneDirection(this.containingGtu);
 
                     record.clearCutOffEnd();
                     iterator.remove(); // can remove from edge, no algorithm needs it anymore in the downstream edge
                     for (Lane nextLane : nexts.keySet())
                     {
                         if (nextLaneDirection != null
                                 && nextLane.getParentLink().equals(nextLaneDirection.getLane().getParentLink())
                                 && !nextLane.equals(nextLaneDirection.getLane()))
                         {
                             // skip this lane as its a not chosen lane on the next link after a lane split
                             continue;
                         }
                         RelativeLane relativeLane = this.relativeLanes.get(record);
                         GTUDirectionality dir = nexts.get(nextLane);
                         RollingLaneStructureRecord next = constructRecord(nextLane, dir, record, RecordLink.DOWN, relativeLane);
                         this.ignoreSet.add(nextLane);
                         next.updateStartDistance(fractionalPosition, this);
                         record.addNext(next);
                         next.addPrev(record);
                         connectLaterally(next, gtuType, modifiedEdge);
                         // check route
                         int from = route == null ? 0 : route.indexOf(next.getFromNode());
                         int to = route == null ? 1 : route.indexOf(next.getToNode());
                         if (to < 0 || to - from != 1)
                         {
                             // not on our route, add some distance and stop
                             splitSet.add(next);
                         }
                         else
                         {
                             // regular edge
                             nextSet.add(next);
                         }
                         modifiedEdge.add(next);
                         // expand upstream over any possible other lane that merges in to this
                         Set<RollingLaneStructureRecord> set = new HashSet<>();
                         set.add(next);
                         expandUpstreamMerge(set, gtuType, fractionalPosition, route);
                     }
                 }
             }
             this.downstreamEdge.addAll(nextSet);
             expand |= !nextSet.isEmpty();
             nextSet.clear();
 
             // split
             expandDownstreamSplit(splitSet, gtuType, fractionalPosition, route);
             splitSet.clear();
 
             // lateral
             Set<RollingLaneStructureRecord> lateralSet =
                     expandLateral(this.downstreamEdge, RecordLink.LATERAL_END, gtuType, fractionalPosition);
             nextSet.addAll(lateralSet);
             expandUpstreamMerge(lateralSet, gtuType, fractionalPosition, route);
 
             // next iteration
             this.downstreamEdge.addAll(nextSet);
             expand |= !nextSet.isEmpty();
             nextSet.clear();
         }
     }
 
     /**
      * Expand the map to include a limited section downstream of a split, regarding links not on the route.
      * @param set Set&lt;RollingLaneStructureRecord&gt;; set of lanes that have been laterally found
      * @param gtuType GTUType; GTU type
      * @param fractionalPosition double; fractional position on reference link
      * @param route Route; route
      * @throws GTUException on exception
      */
     private void expandDownstreamSplit(final Set<RollingLaneStructureRecord> set, final GTUType gtuType,
             final double fractionalPosition, final Route route) throws GTUException
     {
         Map<RollingLaneStructureRecord, Length> prevs = new LinkedHashMap<>();
         Map<RollingLaneStructureRecord, Length> nexts = new LinkedHashMap<>();
         for (RollingLaneStructureRecord record : set)
         {
             prevs.put(record, record.getStartDistance().plus(this.downSplit));
         }
         while (!prevs.isEmpty())
         {
             for (RollingLaneStructureRecord prev : prevs.keySet())
             {
                 Map<Lane, GTUDirectionality> nextLanes = prev.getLane().downstreamLanes(prev.getDirection(), gtuType);
                 RelativeLane relativeLane = this.relativeLanes.get(prev);
                 for (Lane nextLane : nextLanes.keySet())
                 {
                     GTUDirectionality dir = nextLanes.get(nextLane);
                     Node fromNode =
                             dir.isPlus() ? nextLane.getParentLink().getStartNode() : nextLane.getParentLink().getEndNode();
                     Node toNode =
                             dir.isPlus() ? nextLane.getParentLink().getEndNode() : nextLane.getParentLink().getStartNode();
                     int from = route.indexOf(fromNode);
                     int to = route.indexOf(toNode);
                     if (from == -1 || to == -1 || to - from != 1)
                     {
                         RollingLaneStructureRecord next = constructRecord(nextLane, dir, prev, RecordLink.DOWN, relativeLane);
                         next.updateStartDistance(fractionalPosition, this);
                         next.addPrev(prev);
                         prev.addNext(next);
                         connectLaterally(next, gtuType, nexts.keySet());
                         Length downHere = prevs.get(prev);
                         if (next.getStartDistance().si > downHere.si)
                         {
                             next.setCutOffEnd(downHere.minus(next.getStartDistance()));
                         }
                         else
                         {
                             nexts.put(next, downHere);
                         }
                     }
                 }
             }
             prevs = nexts;
             nexts = new LinkedHashMap<>();
         }
     }
 
     /**
      * Expand the map to include a limited section upstream of a merge that is downstream, regarding links not on the route.
      * @param set Set&lt;RollingLaneStructureRecord&gt;; set of lanes that have been laterally found
      * @param gtuType GTUType; GTU type
      * @param fractionalPosition double; fractional position on reference link
      * @param route Route; route of the GTU
      * @throws GTUException on exception
      */
     private void expandUpstreamMerge(final Set<RollingLaneStructureRecord> set, final GTUType gtuType,
             final double fractionalPosition, final Route route) throws GTUException
     {
         Map<RollingLaneStructureRecord, Length> prevs = new LinkedHashMap<>();
         Map<RollingLaneStructureRecord, Length> nexts = new LinkedHashMap<>();
         for (RollingLaneStructureRecord record : set)
         {
             prevs.put(record, record.getStartDistance().plus(this.upMerge)); // upMerge is negative
         }
         while (!prevs.isEmpty())
         {
             for (RollingLaneStructureRecord prev : prevs.keySet())
             {
                 Map<Lane, GTUDirectionality> nextLanes = prev.getLane().upstreamLanes(prev.getDirection(), gtuType);
                 boolean anyAdded = false;
                 for (Lane nextLane : nextLanes.keySet())
                 {
                     GTUDirectionality dir = nextLanes.get(nextLane);
                     Node fromNode =
                             dir.isPlus() ? nextLane.getParentLink().getStartNode() : nextLane.getParentLink().getEndNode();
                     Node toNode =
                             dir.isPlus() ? nextLane.getParentLink().getEndNode() : nextLane.getParentLink().getStartNode();
                     int from = route == null ? 0 : route.indexOf(fromNode);
                     int to = route == null ? 1 : route.indexOf(toNode);
                     // TODO we now assume everything is on the route, but merges could be ok without route
                     // so, without a route we should be able to recognize which upstream 'nextLane' is on the other link
                     if (from == -1 || to == -1 || to - from != 1)
                     {
                         anyAdded = true;
                         RelativeLane relativeLane = this.relativeLanes.get(prev);
                         RollingLaneStructureRecord next =
                                 constructRecord(nextLane, nextLanes.get(nextLane), prev, RecordLink.UP, relativeLane);
                         next.updateStartDistance(fractionalPosition, this);
                         next.addNext(prev);
                         prev.addPrev(next);
                         connectLaterally(next, gtuType, nexts.keySet());
                         Length upHere = prevs.get(prev);
                         if (next.getStartDistance().si < upHere.si)
                         {
                             next.setCutOffStart(upHere.minus(next.getStartDistance()));
                             this.upstreamEdge.add(next);
                         }
                         else
                         {
                             nexts.put(next, upHere);
                         }
                     }
                 }
                 if (!anyAdded && !set.contains(prev))
                 {
                     this.upstreamEdge.add(prev);
                 }
             }
             prevs = nexts;
             nexts = new LinkedHashMap<>();
         }
     }
 
     /**
      * Helper method of various other methods that laterally couples lanes that have been longitudinally found.
      * @param record RollingLaneStructureRecord; longitudinally found lane
      * @param gtuType GTUType; GTU type
      * @param nextSet Set&lt;RollingLaneStructureRecord&gt;; set of records on current build edge
      */
     private void connectLaterally(final RollingLaneStructureRecord record, final GTUType gtuType,
             final Set<RollingLaneStructureRecord> nextSet)
     {
         for (RollingLaneStructureRecord other : nextSet)
         {
             for (LateralDirectionality latDirection : new LateralDirectionality[] { LateralDirectionality.LEFT,
                     LateralDirectionality.RIGHT })
             {
                 if ((latDirection.isLeft() ? other.getLeft() : other.getRight()) == null)
                 {
                     for (Lane otherLane : other.getLane().accessibleAdjacentLanesPhysical(latDirection, gtuType,
                             other.getDirection()))
                     {
                         if (otherLane.equals(record.getLane()))
                         {
                             if (latDirection.isLeft())
                             {
                                 other.setLeft(record, gtuType);
                                 record.setRight(other, gtuType);
                             }
                             else
                             {
                                 other.setRight(record, gtuType);
                                 record.setLeft(other, gtuType);
                             }
                         }
                     }
                 }
             }
         }
     }
 
     /**
      * Creates a lane structure record and adds it to relevant maps.
      * @param lane Lane; lane
      * @param direction GTUDirectionality; direction
      * @param startDistanceSource RollingLaneStructureRecord; source of the start distance
      * @param recordLink RecordLink; record link
      * @param relativeLane RelativeLane; relative lane
      * @return created lane structure record
      */
     private RollingLaneStructureRecord constructRecord(final Lane lane, final GTUDirectionality direction,
             final RollingLaneStructureRecord startDistanceSource, final RecordLink recordLink, final RelativeLane relativeLane)
     {
         RollingLaneStructureRecord record = new RollingLaneStructureRecord(lane, direction, startDistanceSource, recordLink);
         if (!this.relativeLaneMap.containsKey(relativeLane))
         {
             this.relativeLaneMap.put(relativeLane, new LinkedHashSet<>());
         }
         this.relativeLaneMap.get(relativeLane).add(record);
         this.relativeLanes.put(record, relativeLane);
         return record;
     }
 
     /** {@inheritDoc} */
     @Override
     public final LaneStructureRecord getRootRecord()
     {
         return this.root.get();
     }
 
     /**
      * @param time Time; time to obtain the root at
      * @return rootRecord
      */
     public final LaneStructureRecord getRootRecord(final Time time)
     {
         return this.root.get(time);
     }
 
     /** {@inheritDoc} */
     @Override
     public final SortedSet<RelativeLane> getExtendedCrossSection()
     {
         return this.firstRecords.navigableKeySet();
     }
 
     /**
      * Returns the first record on the given lane. This is often a record in the current cross section, but it may be one
      * downstream for a lane that starts further downstream.
      * @param lane RelativeLane; lane
      * @return first record on the given lane, or {@code null} if no such record
      */
     @Override
     public final RollingLaneStructureRecord getFirstRecord(final RelativeLane lane)
     {
         if (this.firstRecords.containsKey(lane))
         {
             return this.firstRecords.get(lane);
         }
         // not in current cross section, get first via downstream
         RelativeLane rel = RelativeLane.CURRENT;
         int dMin = Integer.MAX_VALUE;
         for (RelativeLane relLane : this.crossSectionRecords.keySet())
         {
             if (relLane.getLateralDirectionality().equals(lane.getLateralDirectionality()))
             {
                 int d = lane.getNumLanes() - relLane.getNumLanes();
                 if (d < dMin)
                 {
                     rel = relLane;
                     d = dMin;
                 }
             }
         }
         RollingLaneStructureRecord record = this.crossSectionRecords.get(rel);
         // move downstream until a lateral move is made to the right relative lane
         while (rel.getNumLanes() < lane.getNumLanes())
         {
             RollingLaneStructureRecord adj = lane.getLateralDirectionality().isLeft() ? record.getLeft() : record.getRight();
             if (adj != null)
             {
                 rel = lane.getLateralDirectionality().isLeft() ? rel.getLeft() : rel.getRight();
                 record = adj;
             }
             else if (!record.getNext().isEmpty())
             {
                 LaneDirection laneDir =
                         new LaneDirection(record.getLane(), record.getDirection()).getNextLaneDirection(this.containingGtu);
                 if (laneDir == null)
                 {
                     record = null;
                     break;
                 }
                 RollingLaneStructureRecord chosenNext = null;
                 for (RollingLaneStructureRecord next : record.getNext())
                 {
                     if (next.getLane().equals(laneDir.getLane()))
                     {
                         chosenNext = next;
                         break;
                     }
                 }
                 Throw.when(chosenNext == null, RuntimeException.class,
                         "Unexpected exception while deriving first record not on the cross-section.");
                 record = chosenNext;
             }
             else
             {
                 // reached a dead-end
                 record = null;
                 break;
             }
         }
         if (record != null)
         {
             // now move upstream until we are at x = 0
             while (record.getPrev().size() == 1 && record.getStartDistance().gt0())
             {
                 record = record.getPrev().get(0);
             }
             this.firstRecords.put(lane, record);
         }
         return record;
     }
 
     /**
      * Retrieve objects of a specific type. Returns objects over a maximum length of the look ahead distance downstream from the
      * relative position, or as far as the lane map goes.
      * @param clazz Class&lt;T&gt;; class of objects to find
      * @param gtu LaneBasedGTU; gtu
      * @param pos RelativePosition.TYPE; relative position to start search from
      * @param <T> type of objects to find
      * @return Sorted set of objects of requested type per lane
      * @throws GTUException if lane is not in current set
      */
     @Override
     public final <T extends LaneBasedObject> Map<RelativeLane, SortedSet<Entry<T>>> getDownstreamObjects(final Class<T> clazz,
             final LaneBasedGTU gtu, final RelativePosition.TYPE pos) throws GTUException
     {
         Map<RelativeLane, SortedSet<Entry<T>>> out = new HashMap<>();
         for (RelativeLane relativeLane : this.relativeLaneMap.keySet())
         {
             out.put(relativeLane, getDownstreamObjects(relativeLane, clazz, gtu, pos));
         }
         return out;
     }
 
     /**
      * Retrieve objects on a lane of a specific type. Returns objects over a maximum length of the look ahead distance
      * downstream from the relative position, or as far as the lane map goes.
      * @param lane RelativeLane; lane
      * @param clazz Class&lt;T&gt;; class of objects to find
      * @param gtu LaneBasedGTU; gtu
      * @param pos RelativePosition.TYPE; relative position to start search from
      * @param <T> type of objects to find
      * @return Sorted set of objects of requested type
      * @throws GTUException if lane is not in current set
      */
     @Override
     @SuppressWarnings("unchecked")
     public final <T extends LaneBasedObject> SortedSet<Entry<T>> getDownstreamObjects(final RelativeLane lane,
             final Class<T> clazz, final LaneBasedGTU gtu, final RelativePosition.TYPE pos) throws GTUException
     {
         LaneStructureRecord record = getFirstRecord(lane);
         SortedSet<Entry<T>> set = new TreeSet<>();
         if (record != null)
         {
             double ds = gtu.getRelativePositions().get(pos).getDx().si - gtu.getReference().getDx().si;
             if (record.isDownstreamBranch())
             {
                 // the list is ordered, but only for DIR_PLUS, need to do our own ordering
                 Length minimumPosition;
                 Length maximumPosition;
                 if (record.getDirection().isPlus())
                 {
                     minimumPosition = Length.createSI(ds - record.getStartDistance().si);
                     maximumPosition = Length.createSI(record.getLane().getLength().si);
                 }
                 else
                 {
                     minimumPosition = Length.ZERO;
                     maximumPosition = Length.createSI(record.getLane().getLength().si + record.getStartDistance().si - ds);
                 }
 
                 for (LaneBasedObject object : record.getLane().getLaneBasedObjects(minimumPosition, maximumPosition))
                 {
                     if (clazz.isAssignableFrom(object.getClass())
                             && ((record.getDirection().isPlus() && object.getDirection().isForwardOrBoth())
                                     || (record.getDirection().isMinus() && object.getDirection().isBackwardOrBoth())))
                     {
                         // unchecked, but the above isAssignableFrom assures correctness
                         double distance = record.getDistanceToPosition(object.getLongitudinalPosition()).si - ds;
                         if (distance <= this.lookAhead.si)
                         {
                             set.add(new Entry<>(Length.createSI(distance), (T) object));
                         }
                     }
                 }
             }
             getDownstreamObjectsRecursive(set, record, clazz, ds);
         }
         return set;
     }
 
     /**
      * Retrieve objects on a lane of a specific type. Returns objects over a maximum length of the look ahead distance
      * downstream from the relative position, or as far as the lane map goes. Objects on links not on the route are ignored.
      * @param lane RelativeLane; lane
      * @param clazz Class&lt;T&gt;; class of objects to find
      * @param gtu LaneBasedGTU; gtu
      * @param pos RelativePosition.TYPE; relative position to start search from
      * @param <T> type of objects to find
      * @param route Route; the route
      * @return Sorted set of objects of requested type
      * @throws GTUException if lane is not in current set
      */
     @Override
     public final <T extends LaneBasedObject> SortedSet<Entry<T>> getDownstreamObjectsOnRoute(final RelativeLane lane,
             final Class<T> clazz, final LaneBasedGTU gtu, final RelativePosition.TYPE pos, final Route route)
             throws GTUException
     {
         SortedSet<Entry<T>> set = getDownstreamObjects(lane, clazz, gtu, pos);
         if (route != null)
         {
             Iterator<Entry<T>> iterator = set.iterator();
             while (iterator.hasNext())
             {
                 Entry<T> entry = iterator.next();
                 CrossSectionLink link = entry.getLaneBasedObject().getLane().getParentLink();
                 if (!route.contains(link.getStartNode()) || !route.contains(link.getEndNode())
                         || Math.abs(route.indexOf(link.getStartNode()) - route.indexOf(link.getEndNode())) != 1)
                 {
                     iterator.remove();
                 }
             }
         }
         return set;
     }
 
     /**
      * Recursive search for lane based objects downstream.
      * @param set SortedSet&lt;Entry&lt;T&gt;&gt;; set to store entries into
      * @param record LaneStructureRecord; current record
      * @param clazz Class&lt;T&gt;; class of objects to find
      * @param ds double; distance from reference to chosen relative position
      * @param <T> type of objects to find
      */
     @SuppressWarnings("unchecked")
     private <T extends LaneBasedObject> void getDownstreamObjectsRecursive(final SortedSet<Entry<T>> set,
             final LaneStructureRecord record, final Class<T> clazz, final double ds)
     {
         if (record.getNext().isEmpty() || record.getNext().get(0).getStartDistance().gt(this.lookAhead))
         {
             return;
         }
         for (LaneStructureRecord next : record.getNext())
         {
             if (next.isDownstreamBranch())
             {
                 List<LaneBasedObject> list = next.getLane().getLaneBasedObjects();
                 int iStart, di;
                 if (record.getDirection().isPlus())
                 {
                     iStart = 0;
                     di = 1;
                 }
                 else
                 {
                     iStart = list.size() - 1;
                     di = -1;
                 }
                 for (int i = iStart; i >= 0 & i < list.size(); i += di)
                 {
                     LaneBasedObject object = list.get(i);
                     if (clazz.isAssignableFrom(object.getClass())
                             && ((record.getDirection().isPlus() && object.getDirection().isForwardOrBoth())
                                     || (record.getDirection().isMinus() && object.getDirection().isBackwardOrBoth())))
                     {
                         // unchecked, but the above isAssignableFrom assures correctness
                         double distance = next.getDistanceToPosition(object.getLongitudinalPosition()).si - ds;
                         if (distance <= this.lookAhead.si)
                         {
                             set.add(new Entry<>(Length.createSI(distance), (T) object));
                         }
                         else
                         {
                             return;
                         }
                     }
                 }
             }
             getDownstreamObjectsRecursive(set, next, clazz, ds);
         }
     }
 
     /**
      * Retrieve objects of a specific type. Returns objects over a maximum length of the look ahead distance downstream from the
      * relative position, or as far as the lane map goes. Objects on links not on the route are ignored.
      * @param clazz Class&lt;T&gt;; class of objects to find
      * @param gtu LaneBasedGTU; gtu
      * @param pos RelativePosition.TYPE; relative position to start search from
      * @param <T> type of objects to find
      * @param route Route; the route
      * @return Sorted set of objects of requested type per lane
      * @throws GTUException if lane is not in current set
      */
     @Override
     public final <T extends LaneBasedObject> Map<RelativeLane, SortedSet<Entry<T>>> getDownstreamObjectsOnRoute(
             final Class<T> clazz, final LaneBasedGTU gtu, final RelativePosition.TYPE pos, final Route route)
             throws GTUException
     {
         Map<RelativeLane, SortedSet<Entry<T>>> out = new HashMap<>();
         for (RelativeLane relativeLane : this.relativeLaneMap.keySet())
         {
             out.put(relativeLane, getDownstreamObjectsOnRoute(relativeLane, clazz, gtu, pos, route));
         }
         return out;
     }
 
     /**
      * Retrieve objects on a lane of a specific type. Returns upstream objects from the relative position for as far as the lane
      * map goes. Distances to upstream objects are given as positive values.
      * @param lane RelativeLane; lane
      * @param clazz Class&lt;T&gt;; class of objects to find
      * @param gtu LaneBasedGTU; gtu
      * @param pos RelativePosition.TYPE; relative position to start search from
      * @param <T> type of objects to find
      * @return Sorted set of objects of requested type
      * @throws GTUException if lane is not in current set
      */
     @Override
     @SuppressWarnings("unchecked")
     public final <T extends LaneBasedObject> SortedSet<Entry<T>> getUpstreamObjects(final RelativeLane lane,
             final Class<T> clazz, final LaneBasedGTU gtu, final RelativePosition.TYPE pos) throws GTUException
     {
         SortedSet<Entry<T>> set = new TreeSet<>();
         LaneStructureRecord record = this.getFirstRecord(lane);
         if (record.getStartDistance().gt0())
         {
             return set; // this lane is only downstream
         }
         Length ds = gtu.getReference().getDx().minus(gtu.getRelativePositions().get(pos).getDx());
         // the list is ordered, but only for DIR_PLUS, need to do our own ordering
         Length minimumPosition;
         Length maximumPosition;
         if (record.getDirection().isPlus())
         {
             minimumPosition = Length.ZERO;
             maximumPosition = record.getStartDistance().neg().minus(ds);
         }
         else
         {
             minimumPosition = record.getLane().getLength().plus(record.getStartDistance()).plus(ds);
             maximumPosition = record.getLane().getLength();
         }
         Length distance;
         for (LaneBasedObject object : record.getLane().getLaneBasedObjects(minimumPosition, maximumPosition))
         {
             if (clazz.isAssignableFrom(object.getClass())
                     && ((record.getDirection().isPlus() && object.getDirection().isForwardOrBoth())
                             || (record.getDirection().isMinus() && object.getDirection().isBackwardOrBoth())))
             {
                 distance = record.getDistanceToPosition(object.getLongitudinalPosition()).neg().minus(ds);
                 // unchecked, but the above isAssignableFrom assures correctness
                 set.add(new Entry<>(distance, (T) object));
             }
         }
         getUpstreamObjectsRecursive(set, record, clazz, ds);
         return set;
     }
 
     /**
      * Recursive search for lane based objects upstream.
      * @param set SortedSet&lt;Entry&lt;T&gt;&gt;; set to store entries into
      * @param record LaneStructureRecord; current record
      * @param clazz Class&lt;T&gt;; class of objects to find
      * @param ds Length; distance from reference to chosen relative position
      * @param <T> type of objects to find
      */
     @SuppressWarnings("unchecked")
     private <T extends LaneBasedObject> void getUpstreamObjectsRecursive(final SortedSet<Entry<T>> set,
             final LaneStructureRecord record, final Class<T> clazz, final Length ds)
     {
         for (LaneStructureRecord prev : record.getPrev())
         {
             Length distance;
             for (LaneBasedObject object : prev.getLane().getLaneBasedObjects())
             {
                 if (clazz.isAssignableFrom(object.getClass())
                         && ((record.getDirection().isPlus() && object.getDirection().isForwardOrBoth())
                                 || (record.getDirection().isMinus() && object.getDirection().isBackwardOrBoth())))
                 {
                     distance = prev.getDistanceToPosition(object.getLongitudinalPosition()).neg().minus(ds);
                     // unchecked, but the above isAssignableFrom assures correctness
                     set.add(new Entry<>(distance, (T) object));
                 }
             }
             getUpstreamObjectsRecursive(set, prev, clazz, ds);
         }
     }
 
     /** {@inheritDoc} */
     @Override
     public final String toString()
     {
         return "LaneStructure [rootLSR=" + this.root + "]";
     }
 
     /**
      * AnimationAccess provides access to a number of private fields in the structure, which should only be used read-only! <br>
      * <br>
      * Copyright (c) 2003-2019 Delft University of Technology, Jaffalaan 5, 2628 BX Delft, the Netherlands. All rights reserved.
      * See for project information <a href="https://www.simulation.tudelft.nl/" target="_blank">www.simulation.tudelft.nl</a>.
      * The source code and binary code of this software is proprietary information of Delft University of Technology.
      * @author <a href="https://www.tudelft.nl/averbraeck" target="_blank">Alexander Verbraeck</a>
      */
     public class AnimationAccess
     {
         /**
          * @return the lane structure records of the cross section
          */
         @SuppressWarnings("synthetic-access")
         public TreeMap<RelativeLane, RollingLaneStructureRecord> getCrossSectionRecords()
         {
             return RollingLaneStructure.this.crossSectionRecords;
         }
 
         /**
          * @return the upstream edge
          */
         @SuppressWarnings("synthetic-access")
         public Set<RollingLaneStructureRecord> getUpstreamEdge()
         {
             return RollingLaneStructure.this.upstreamEdge;
         }
 
         /**
          * @return the downstream edge
          */
         @SuppressWarnings("synthetic-access")
         public Set<RollingLaneStructureRecord> getDownstreamEdge()
         {
             return RollingLaneStructure.this.downstreamEdge;
         }
     }
 }