package org.opentrafficsim.road.gtu.lane.tactical.util;
   
   import static org.opentrafficsim.core.gtu.behavioralcharacteristics.AbstractParameterType.Check.ATLEASTONE;
   import static org.opentrafficsim.core.gtu.behavioralcharacteristics.AbstractParameterType.Check.POSITIVE;
   
   import java.io.Serializable;
   import java.util.ArrayList;
   import java.util.HashMap;
   import java.util.HashSet;
  import java.util.Iterator;
  import java.util.List;
  import java.util.Map;
  import java.util.Set;
  import java.util.SortedMap;
  import java.util.SortedSet;
  import java.util.TreeMap;
  import java.util.UUID;
  
  import org.djunits.unit.AccelerationUnit;
  import org.djunits.unit.LengthUnit;
  import org.djunits.unit.TimeUnit;
  import org.djunits.value.vdouble.scalar.Acceleration;
  import org.djunits.value.vdouble.scalar.Duration;
  import org.djunits.value.vdouble.scalar.Length;
  import org.djunits.value.vdouble.scalar.Speed;
  import org.djunits.value.vdouble.scalar.Time;
  import org.opentrafficsim.core.gtu.GTUException;
  import org.opentrafficsim.core.gtu.behavioralcharacteristics.BehavioralCharacteristics;
  import org.opentrafficsim.core.gtu.behavioralcharacteristics.ParameterException;
  import org.opentrafficsim.core.gtu.behavioralcharacteristics.ParameterTypeDouble;
  import org.opentrafficsim.core.gtu.behavioralcharacteristics.ParameterTypeDuration;
  import org.opentrafficsim.core.gtu.behavioralcharacteristics.ParameterTypeLength;
  import org.opentrafficsim.core.gtu.behavioralcharacteristics.ParameterTypes;
  import org.opentrafficsim.core.network.Node;
  import org.opentrafficsim.core.network.route.Route;
  import org.opentrafficsim.road.gtu.lane.RoadGTUTypes;
  import org.opentrafficsim.road.gtu.lane.perception.headway.AbstractHeadwayGTU;
  import org.opentrafficsim.road.gtu.lane.perception.headway.HeadwayConflict;
  import org.opentrafficsim.road.gtu.lane.perception.headway.HeadwayGTUSimple;
  import org.opentrafficsim.road.gtu.lane.perception.headway.HeadwayStopLine;
  import org.opentrafficsim.road.gtu.lane.tactical.following.CarFollowingModel;
  import org.opentrafficsim.road.network.lane.CrossSectionLink;
  import org.opentrafficsim.road.network.lane.conflict.ConflictRule;
  import org.opentrafficsim.road.network.lane.conflict.ConflictType;
  import org.opentrafficsim.road.network.speed.SpeedLimitInfo;
  
  import nl.tudelft.simulation.language.Throw;
  
  /**
   * This class implements default behavior for intersection conflicts for use in tactical planners.
   * <p>
   * Copyright (c) 2013-2016 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/current/license.html">OpenTrafficSim License</a>.
   * <p>
   * @version $Revision$, $LastChangedDate$, by $Author$, initial version Jun 3, 2016 <br>
   * @author <a href="http://www.tbm.tudelft.nl/averbraeck">Alexander Verbraeck</a>
   * @author <a href="http://www.tudelft.nl/pknoppers">Peter Knoppers</a>
   * @author <a href="http://www.transport.citg.tudelft.nl">Wouter Schakel</a>
   */
  // TODO conflict over multiple lanes (longitudinal in own direction)
  // TODO stop length depending on speed?
  // TODO vehicle generation at speed in T-junction demo
  // TODO turbo roundabout demo
  // TODO a) yielding while having priority happens only when leaders is standing still on conflict (then its useless...)
  // b) two vehicles can remain upstream of merge if vehicle stands on merge but leaves some space to move
  // probably 1 is yielding, and 1 is courtesy yielding as the other stands still
  // c) they might start moving together and collide further down (no response to negative headway on merge)
  public final class ConflictUtil
  {
  
      /** Minimum time gap between events. */
      public static final ParameterTypeDuration MIN_GAP = new ParameterTypeDuration("minGap", "Minimum gap for conflicts.",
              new Duration(0.000001, TimeUnit.SECOND), POSITIVE);
  
      /** Stopping distance at conflicts. */
      public static final ParameterTypeLength S0_CONF =
              new ParameterTypeLength("s0 conf", "Stopping distance at conflicts.", new Length(1.5, LengthUnit.METER), POSITIVE);
  
      /** Multiplication factor on time for conservative assessment. */
      public static final ParameterTypeDouble TIME_FACTOR =
              new ParameterTypeDouble("timeFactor", "Safety factor on estimated time.", 1.1, ATLEASTONE);
  
      /** Area before stop line where one is considered arrived at the intersection. */
      public static final ParameterTypeLength STOP_AREA =
              new ParameterTypeLength("stopArea", "Area before stop line where one is considered arrived at the intersection.",
                      new Length(4, LengthUnit.METER), POSITIVE);
  
      /** Time step for free acceleration anticipation. */
      private static final Duration TIME_STEP = new Duration(0.5, TimeUnit.SI);
  
      /** Acceleration that is equal to ignoring. */
      private static final Acceleration IGNORE = new Acceleration(Double.MAX_VALUE, AccelerationUnit.SI);
  
      /**
       * Do not instantiate.
       */
      private ConflictUtil()
      {
          //
     }
 
     /**
      * Approach conflicts by applying appropriate acceleration (or deceleration). The model may yield for a vehicle even while
      * having priority. Such a 'yield plan' is remembered in <tt>YieldPlans</tt>. By forwarding the same <tt>YieldPlans</tt> for
      * a GTU consistency of such plans is provided. If any conflict is not accepted to pass, stopping before a more upstream
      * conflict is applied if there not sufficient stopping length in between conflicts.
      * @param behavioralCharacteristics behavioral characteristics
      * @param conflicts set of conflicts to approach
      * @param leaders leading vehicles
      * @param carFollowingModel car-following model
      * @param vehicleLength length of vehicle
      * @param speed current speed
      * @param acceleration current acceleration
      * @param speedLimitInfo speed limit info
      * @param conflictPlans set of plans for conflict
      * @return acceleration appropriate for approaching the conflicts
      * @throws GTUException in case of an unsupported conflict rule
      * @throws ParameterException if a parameter is not defined or out of bounds
      */
     @SuppressWarnings("checkstyle:parameternumber")
     public static Acceleration approachConflicts(final BehavioralCharacteristics behavioralCharacteristics,
             final SortedSet<HeadwayConflict> conflicts, final SortedSet<AbstractHeadwayGTU> leaders,
             final CarFollowingModel carFollowingModel, final Length vehicleLength, final Speed speed,
             final Acceleration acceleration, final SpeedLimitInfo speedLimitInfo, final ConflictPlans conflictPlans)
             throws GTUException, ParameterException
     {
 
         Acceleration a = IGNORE;
         if (conflicts.isEmpty())
         {
             return a;
         }
 
         conflictPlans.cleanYieldPlans();
         List<Length> prevStarts = new ArrayList<>();
         List<Length> prevEnds = new ArrayList<>();
 
         for (HeadwayConflict conflict : conflicts)
         {
 
             // adjust acceleration for situations where stopping might not be required
             if (conflict.isCrossing())
             {
                 // avoid collision if crossing is occupied
                 a = Acceleration.min(a,
                         avoidCrossingCollision(behavioralCharacteristics, conflict, carFollowingModel, speed, speedLimitInfo));
             }
             else
             {
                 // follow leading GTUs on merge or split
                 a = Acceleration.min(a, followConflictingLeaderOnMergeOrSplit(conflict, behavioralCharacteristics,
                         carFollowingModel, speed, speedLimitInfo));
             }
             if (conflict.getDistance().lt(Length.ZERO))
             {
                 // ignore conflicts we are on (i.e. negative distance to start of conflict)
                 continue;
             }
 
             // determine if we need to stop
             boolean stop;
             switch (conflict.getConflictRule())
             {
                 case PRIORITY:
                 {
                     stop = stopForPriorityConflict(conflict, leaders, speed, vehicleLength, behavioralCharacteristics,
                             conflictPlans);
                     break;
                 }
                 case GIVE_WAY:
                 {
                     stop = stopForGiveWayConflict(conflict, leaders, speed, acceleration, vehicleLength,
                             behavioralCharacteristics, speedLimitInfo, carFollowingModel);
                     break;
                 }
                 case STOP:
                 {
                     stop = stopForStopConflict(conflict, leaders, speed, acceleration, vehicleLength, behavioralCharacteristics,
                             speedLimitInfo, carFollowingModel);
                     break;
                 }
                 case ALL_STOP:
                 {
                     stop = stopForAllStopConflict(conflict, conflictPlans);
                     break;
                 }
                 case SPLIT:
                 {
                     stop = false; // skipped anyway
                     break;
                 }
                 default:
                 {
                     throw new GTUException("Unsupported conflict rule encountered while approaching conflicts.");
                 }
             }
 
             // stop if required, account for upstream conflicts to keep clear
             if (!conflict.getConflictType().equals(ConflictType.SPLIT))
             {
 
                 if (stop)
                 {
                     prevStarts.add(conflict.getDistance());
                     // stop for first conflict looking upstream of this blocked conflict that allows sufficient space
                     int j = 0; // most upstream conflict if not in between conflicts
                     for (int i = prevEnds.size() - 1; i >= 0; i--) // downstream to upstream
                     {
                         // note, at this point prevStarts contains one more conflict than prevEnds
                         if (prevStarts.get(i + 1).minus(prevEnds.get(i))
                                 .gt(passableDistance(Speed.ZERO, vehicleLength, behavioralCharacteristics)))
                         {
                             j = i + 1;
                             break;
                         }
                     }
 
                     // TODO
                     // if this lowers our acceleration, we need to check if we are able to pass upstream conflicts still in time
 
                     // stop for j'th conflict, if deceleration is too strong, for next one
                     behavioralCharacteristics.setParameter(ParameterTypes.S0, behavioralCharacteristics.getParameter(S0_CONF));
                     Acceleration aCF = new Acceleration(Double.NEGATIVE_INFINITY, AccelerationUnit.SI);
                     while (aCF.si < -6.0 && j < prevStarts.size())
                     {
                         aCF = Acceleration.max(aCF, CarFollowingUtil.stop(carFollowingModel, behavioralCharacteristics, speed,
                                 speedLimitInfo, prevStarts.get(j)));
                         j++;
                     }
                     behavioralCharacteristics.resetParameter(ParameterTypes.S0);
                     a = Acceleration.min(a, aCF);
                     break;
                 }
                 if (conflict.getConflictRule().equals(ConflictRule.GIVE_WAY)
                         || conflict.getConflictRule().equals(ConflictRule.STOP))
                 {
                     prevStarts.add(conflict.getDistance());
                     prevEnds.add(conflict.getDistance().plus(conflict.getLength()));
                 }
             }
 
         }
 
         if (a.si < -6.0)
         {
             return IGNORE;
         }
         return a;
     }
 
     /**
      * Determines acceleration for following conflicting vehicles <i>on</i> a merge or split conflict.
      * @param conflict merge or split conflict
      * @param behavioralCharacteristics behavioral characteristics
      * @param carFollowingModel car-following model
      * @param speed current speed
      * @param speedLimitInfo speed limit info
      * @return acceleration for following conflicting vehicles <i>on</i> a merge or split conflict
      * @throws ParameterException if a parameter is not given or out of bounds
      */
     private static Acceleration followConflictingLeaderOnMergeOrSplit(final HeadwayConflict conflict,
             final BehavioralCharacteristics behavioralCharacteristics, final CarFollowingModel carFollowingModel,
             final Speed speed, final SpeedLimitInfo speedLimitInfo) throws ParameterException
     {
         // ignore if no conflicting GTU's
         if (conflict.getDownstreamConflictingGTUs().isEmpty())
         {
             return IGNORE;
         }
         // get the most upstream GTU to consider
         AbstractHeadwayGTU c = conflict.getDownstreamConflictingGTUs().first();
         if (c.isAhead())
         {
             // conflict GTU completely downstream of conflict (i.e. regular car-following, ignore here)
             return IGNORE;
         }
         // conflict GTU (partially) on the conflict
         // {@formatter:off}
         // ______________________________________________ 
         //   ___      virtual headway   |  ___  |
         //  |___|(-----------------------)|___|(vehicle from south, on lane from south)
         // _____________________________|_______|________
         //                              /       / 
         //                             /       /
         // {@formatter:on}
         Length virtualHeadway = conflict.getDistance().plus(c.getOverlapRear());
         if (virtualHeadway.le(Length.ZERO) && conflict.getDistance().le(Length.ZERO))
         {
             // conflict GTU downstream of start of conflict, but upstream of us
             return IGNORE;
         }
         // follow leader
         SortedMap<Length, Speed> leaders = new TreeMap<>();
         leaders.put(virtualHeadway, c.getSpeed());
         Acceleration a = carFollowingModel.followingAcceleration(behavioralCharacteristics, speed, speedLimitInfo, leaders);
         // if conflicting GTU is partially upstream of the conflict and at (near) stand-still, stop for the conflict rather than
         // following the tail of the conflicting GTU
         if (conflict.isMerge() && virtualHeadway.lt(conflict.getDistance()))
         {
             // {@formatter:off}
             /*
              * ______________________________________________
              *    ___    stop for conflict  |       | 
              *   |___|(--------------------)|   ___ |
              * _____________________________|__/  /_|________ 
              *                              / /__/  /
              *                             /       /
              */
             // {@formatter:on}
             behavioralCharacteristics.setParameter(ParameterTypes.S0, behavioralCharacteristics.getParameter(S0_CONF));
             Acceleration aStop = CarFollowingUtil.stop(carFollowingModel, behavioralCharacteristics, speed, speedLimitInfo,
                     conflict.getDistance());
             behavioralCharacteristics.resetParameter(ParameterTypes.S0);
             a = Acceleration.max(a, aStop); // max, which ever allows the largest acceleration
         }
         return a;
     }
 
     /**
      * Determines an acceleration required to avoid a collision with GTUs <i>on</i> a crossing conflict.
      * @param behavioralCharacteristics behavioral characteristics
      * @param conflict conflict
      * @param carFollowingModel car-following model
      * @param speed current speed
      * @param speedLimitInfo speed limit info
      * @return acceleration required to avoid a collision
      * @throws ParameterException if parameter is not defined
      */
     private static Acceleration avoidCrossingCollision(final BehavioralCharacteristics behavioralCharacteristics,
             final HeadwayConflict conflict, final CarFollowingModel carFollowingModel, final Speed speed,
             final SpeedLimitInfo speedLimitInfo) throws ParameterException
     {
 
         // TODO only within visibility
         List<AbstractHeadwayGTU> conflictingGTUs = new ArrayList<>();
         for (AbstractHeadwayGTU gtu : conflict.getUpstreamConflictingGTUs())
         {
             if (isOnRoute(conflict.getConflictingLink(), gtu))
             {
                 // first upstream vehicle on route to this conflict
                 conflictingGTUs.add(gtu);
                 break;
             }
         }
         for (AbstractHeadwayGTU gtu : conflict.getDownstreamConflictingGTUs())
         {
             if (gtu.isParallel())
             {
                 conflictingGTUs.add(gtu);
             }
             else
             {
                 // vehicles beyond conflict are not a thread
                 break;
             }
         }
 
         if (conflictingGTUs.isEmpty())
         {
             return IGNORE;
         }
 
         Acceleration a = IGNORE;
         for (AbstractHeadwayGTU conflictingGTU : conflictingGTUs)
         {
             AnticipationInfo tteC;
             Length distance;
             if (conflictingGTU.isParallel())
             {
                 tteC = new AnticipationInfo(Duration.ZERO, conflictingGTU.getSpeed());
                 distance = conflictingGTU.getOverlapRear().abs().plus(conflictingGTU.getOverlap())
                         .plus(conflictingGTU.getOverlapFront().abs());
             }
             else
             {
                 tteC = AnticipationInfo.anticipateMovement(conflictingGTU.getDistance(), conflictingGTU.getSpeed(),
                         Acceleration.ZERO);
                 distance = conflictingGTU.getDistance().plus(conflict.getLength()).plus(conflictingGTU.getLength());
             }
             AnticipationInfo ttcC = AnticipationInfo.anticipateMovement(distance, conflictingGTU.getSpeed(), Acceleration.ZERO);
             AnticipationInfo tteO = AnticipationInfo.anticipateMovementFreeAcceleration(conflict.getDistance(), speed,
                     behavioralCharacteristics, carFollowingModel, speedLimitInfo, TIME_STEP);
             // enter before cleared
             // TODO safety factor?
             if (tteC.getDuration().lt(tteO.getDuration()) && tteO.getDuration().lt(ttcC.getDuration()))
             {
                 if (!conflictingGTU.getSpeed().eq(Speed.ZERO))
                 {
                     // solve parabolic speed profile s = v*t + .5*a*t*t, a =
                     double acc = 2 * (conflict.getDistance().si - speed.si * ttcC.getDuration().si)
                             / (ttcC.getDuration().si * ttcC.getDuration().si);
                     // time till zero speed > time to avoid conflict?
                     if (speed.si / -acc > ttcC.getDuration().si)
                     {
                         a = Acceleration.min(a, new Acceleration(acc, AccelerationUnit.SI));
                     }
                     else
                     {
                         // will reach zero speed ourselves
                         a = Acceleration.min(a, CarFollowingUtil.stop(carFollowingModel, behavioralCharacteristics, speed,
                                 speedLimitInfo, conflict.getDistance()));
                     }
                 }
                 // conflicting vehicle stand-still, ignore even at conflict
             }
         }
         return a;
     }
 
     /**
      * Approach a priority conflict. Stopping is applied to give way to conflicting traffic in case congestion is present on the
      * own lane. This is courtesy yielding.
      * @param conflict conflict to approach
      * @param leaders leading vehicles in own lane
      * @param speed current speed
      * @param vehicleLength vehicle length
      * @param behavioralCharacteristics behavioral characteristics
      * @param yieldPlans set of plans for yielding with priority
      * @return whether to stop for this conflict
      * @throws ParameterException if parameter B is not defined
      */
     private static boolean stopForPriorityConflict(final HeadwayConflict conflict, final SortedSet<AbstractHeadwayGTU> leaders,
             final Speed speed, final Length vehicleLength, final BehavioralCharacteristics behavioralCharacteristics,
             final ConflictPlans yieldPlans) throws ParameterException
     {
 
         // Escape if no conflicting traffic or traffic ahead
         if (leaders.isEmpty() || conflict.getUpstreamConflictingGTUs().isEmpty())
         {
             // no leader, or no conflicting vehicle
             return false;
         }
 
         // Consider factors where we don't yield, even if this was our plan before
         Length distance = conflict.getDistance().minus(leaders.first().getDistance())
                 .plus(passableDistance(speed, vehicleLength, behavioralCharacteristics));
         if (conflict.isCrossing())
         {
             // Merge is cleared at start, crossing at end
             distance = distance.plus(conflict.getLength());
         }
         AnticipationInfo ttpD =
                 AnticipationInfo.anticipateMovement(distance, leaders.first().getSpeed(), leaders.first().getAcceleration());
         AbstractHeadwayGTU first = conflict.getUpstreamConflictingGTUs().first();
         boolean conflictGtuCanReachConflict =
                 first.getDistance().lt(behavioralCharacteristics.getParameter(STOP_AREA)) || first.getSpeed().gt(Speed.ZERO);
         boolean leaderStandsOnConflict = leaders.first().getSpeed().eq(Speed.ZERO) && !leaders.first().isAhead();
         // Do not courtesy yield, even if this was the plan, if:
         // 1) Leader leaves conflict passable now
         // 2) Leader stands still on conflict (no point in yielding, conflict is blocked anyway)
         // 3) Conflict vehicle stand still away from conflict (i.e. blocked by something else)
         if (ttpD.getDuration().eq(Duration.ZERO) || leaderStandsOnConflict || !conflictGtuCanReachConflict)
         {
             return false;
         }
 
         // If yielding was the plan, keep yielding
         if (yieldPlans.isYieldPlan(conflict, first))
         {
             yieldPlans.setYieldPlan(conflict, first); // this makes sure the plan is not cleared
             return true;
         }
 
         // Check factors to initiate a courtesy yield plan (in parts, to not calculate it all if not needed)
         // 1) Conflict vehicle does not stand still away from conflict (i.e. might recht conflict)
         // 2) Leader is ahead of conflict or still moving
         if (conflictGtuCanReachConflict && !leaderStandsOnConflict)
         {
             AnticipationInfo ttcC = AnticipationInfo.anticipateMovementFreeAcceleration(
                     first.getDistance().plus(conflict.getConflictingLength()).plus(first.getLength()), first.getSpeed(),
                     first.getBehavioralCharacteristics(), first.getCarFollowingModel(), first.getSpeedLimitInfo(), TIME_STEP);
             // 3) Conflict vehicle will pass conflict before leader makes it passable, we may courtesy yield without loss
             if (ttpD.getDuration().ge(ttcC.getDuration()))// .multiplyBy(behavioralCharacteristics.getParameter(TIME_FACTOR))
             // .plus(behavioralCharacteristics.getParameter(MIN_GAP))))
             {
                 // 4) Acceleration (constant) is comfortable (at initialization of courtesy yield)
                 Acceleration b = behavioralCharacteristics.getParameter(ParameterTypes.B);
                 Acceleration bReq = new Acceleration(.5 * speed.si * speed.si / conflict.getDistance().si, AccelerationUnit.SI);
                 if (bReq.lt(b))
                 {
                     yieldPlans.setYieldPlan(conflict, first);
                     return true;
                 }
             }
         }
 
         // No initialization of courtesy yield plan
         return false;
 
     }
 
     /**
      * Approach a give-way conflict.
      * @param conflict conflict
      * @param leaders leaders
      * @param speed current speed
      * @param acceleration current acceleration
      * @param vehicleLength vehicle length
      * @param behavioralCharacteristics behavioral characteristics
      * @param speedLimitInfo speed limit info
      * @param carFollowingModel car-following model
      * @return whether to stop for this conflict
      * @throws ParameterException if a parameter is not defined
      */
     @SuppressWarnings("checkstyle:parameternumber")
     private static boolean stopForGiveWayConflict(final HeadwayConflict conflict, final SortedSet<AbstractHeadwayGTU> leaders,
             final Speed speed, final Acceleration acceleration, final Length vehicleLength,
             final BehavioralCharacteristics behavioralCharacteristics, final SpeedLimitInfo speedLimitInfo,
             final CarFollowingModel carFollowingModel) throws ParameterException
     {
 
         // TODO conflicting vehicle on conflict, but will leave sooner then we enter, so no problem?
         if (conflict.getConflictType().equals(ConflictType.CROSSING) && !conflict.getDownstreamConflictingGTUs().isEmpty()
                 && conflict.getDownstreamConflictingGTUs().first().isParallel())
         {
             // vehicle on the conflict
             return true;
         }
 
         // Get data independent of conflicting vehicle
         // parameters
         Acceleration b = behavioralCharacteristics.getParameter(ParameterTypes.B).neg();
         double f = behavioralCharacteristics.getParameter(TIME_FACTOR);
         Duration gap = behavioralCharacteristics.getParameter(MIN_GAP);
         // time till conflict is cleared
         Length distance = conflict.getDistance().plus(vehicleLength);
         if (conflict.isCrossing())
         {
             // merge is cleared at start, crossing at end
             distance = distance.plus(conflict.getLength());
         }
         // based on current acceleration, but limited by free acceleration
         // TODO maybe only constant acceleration? What did MOTUS do?
         AnticipationInfo ttcOa = AnticipationInfo.anticipateMovementFreeAcceleration(distance, speed, behavioralCharacteristics,
                 carFollowingModel, speedLimitInfo, TIME_STEP);
         AnticipationInfo ttcO;
         if (acceleration.lt(Acceleration.ZERO))
         {
             AnticipationInfo ttcOb = AnticipationInfo.anticipateMovement(distance, speed, acceleration);
             ttcO = ttcOa.getDuration().gt(ttcOb.getDuration()) ? ttcOa : ttcOb;
         }
         else
         {
             ttcO = ttcOa;
         }
         // time till downstream vehicle will make the conflict passible, under constant speed or safe deceleration
         AnticipationInfo ttpDz = null;
         AnticipationInfo ttpDs = null;
         if (conflict.isCrossing())
         {
             if (!leaders.isEmpty())
             {
                 distance = conflict.getDistance().minus(leaders.first().getDistance()).plus(conflict.getLength())
                         .plus(passableDistance(Speed.ZERO, vehicleLength, behavioralCharacteristics));
                 ttpDz = AnticipationInfo.anticipateMovement(distance, leaders.first().getSpeed(), Acceleration.ZERO);
                 // TODO not b but b_critical?
                 ttpDs = AnticipationInfo.anticipateMovement(distance, leaders.first().getSpeed(), b);
                 if (Double.isInfinite(ttpDs.getDuration().si))
                 {
                     // if leader decelerates to stand-still, not sufficient space after conflict
                     // stop, even without conflicting vehicles
                     return true;
                 }
             }
             else
             {
                 // no leader so conflict is passible within a duration of 0
                 ttpDz = new AnticipationInfo(Duration.ZERO, Speed.ZERO);
                 ttpDs = new AnticipationInfo(Duration.ZERO, Speed.ZERO);
             }
         }
 
         List<AbstractHeadwayGTU> conflictingVehicles = new ArrayList<>();
         if (!conflict.getUpstreamConflictingGTUs().isEmpty())
         {
             for (AbstractHeadwayGTU vehicle : conflict.getUpstreamConflictingGTUs())
             {
                 if (isOnRoute(conflict.getConflictingLink(), vehicle))
                 {
                     conflictingVehicles.add(vehicle);
                 }
             }
         }
         else
         {
             // none within visibility, assume a conflicting vehicle just outside of visibility driving at speed limit
             try
             {
                 HeadwayGTUSimple conflictGtu = new HeadwayGTUSimple("virtual " + UUID.randomUUID().toString(), RoadGTUTypes.CAR,
                         conflict.getConflictingVisibility(), new Length(4.0, LengthUnit.SI),
                         conflict.getConflictingSpeedLimit(), Acceleration.ZERO);
                 conflictingVehicles.add(conflictGtu);
             }
             catch (GTUException exception)
             {
                 throw new RuntimeException("Could not create a virtual conflicting vehicle at visibility range.", exception);
             }
         }
 
         // Loop over conflicting vehicles
         for (AbstractHeadwayGTU conflictingVehicle : conflictingVehicles)
         {
 
             // time till conflict vehicle will enter, under free acceleration and safe deceleration
             // TODO what does the c stand for? not constant acceleration, i.e. also free acceleration is used
             AnticipationInfo tteCc;
             if (conflictingVehicle instanceof HeadwayGTUSimple)
             {
                 tteCc = AnticipationInfo.anticipateMovement(conflictingVehicle.getDistance(), conflictingVehicle.getSpeed(),
                         conflictingVehicle.getAcceleration());
             }
             else
             {
                 BehavioralCharacteristics bc = conflictingVehicle.getBehavioralCharacteristics();
                 SpeedLimitInfo sli = conflictingVehicle.getSpeedLimitInfo();
                 CarFollowingModel cfm = conflictingVehicle.getCarFollowingModel();
                 // Constant acceleration creates inf at stand still, triggering passing trough a congested stream
                 // tteCc = AnticipationInfo.anticipateMovement(conflictingVehicle.getDistance(), conflictingVehicle.getSpeed(),
                 // conflictingVehicle.getAcceleration());
                 tteCc = AnticipationInfo.anticipateMovementFreeAcceleration(conflictingVehicle.getDistance(),
                         conflictingVehicle.getSpeed(), bc, cfm, sli, TIME_STEP);
             }
             AnticipationInfo tteCs =
                     AnticipationInfo.anticipateMovement(conflictingVehicle.getDistance(), conflictingVehicle.getSpeed(), b);
 
             // check gap
             if (conflict.isMerge())
             {
 
                 // Merge, will be each others followers, add time to overcome speed difference
                 double vSelf = ttcO.getEndSpeed().si;
                 double speedDiff = conflictingVehicle.getSpeed().si - vSelf;
                 speedDiff = speedDiff > 0 ? speedDiff : 0;
                 Duration additionalTime = new Duration(speedDiff / -b.si, TimeUnit.SI);
                 // check if conflict vehicle will be upstream after that time, position beyond conflict after additional time
                 double followerFront = conflictingVehicle.getSpeed().si * ttcO.getDuration().si
                         - conflictingVehicle.getDistance().si + (conflictingVehicle.getSpeed().si * additionalTime.si
                                 + 0.5 * b.si * additionalTime.si * additionalTime.si);
                 double ownRear = vSelf * additionalTime.si; // constant speed after clearing
                 Duration tMax = behavioralCharacteristics.getParameter(ParameterTypes.TMAX);
                 Length s0 = behavioralCharacteristics.getParameter(ParameterTypes.S0);
                 // 1) will clear the conflict after the conflict vehicle enters
                 // 2) not sufficient time to overcome speed difference
                 // 3) conflict vehicle will be too near after adjusting speed
                 if (ttcO.getDuration().multiplyBy(f).plus(gap).gt(tteCc.getDuration())
                         || ttcOa.getDuration().plus(additionalTime).multiplyBy(f).plus(gap).gt(tteCs.getDuration())
                         || ownRear < (followerFront + (tMax.si + gap.si) * vSelf + s0.si) * f)
                 {
                     return true;
                 }
 
             }
             else if (conflict.isCrossing())
             {
 
                 // Crossing, stop if order of events is not ok
                 // 1) downstream vehicle must supply sufficient space before conflict vehicle will enter
                 // 2) must clear the conflict before the conflict vehicle will enter
                 // 3) if leader decelerates with b??, conflict vehicle should be able to safely delay entering conflict
                 if (ttpDz.getDuration().multiplyBy(f).plus(gap).gt(tteCc.getDuration())
                         || ttcOa.getDuration().multiplyBy(f).plus(gap).gt(tteCc.getDuration())
                         || ttpDs.getDuration().multiplyBy(f).plus(gap).gt(tteCs.getDuration()))
                 {
                     return true;
                 }
 
             }
             else
             {
                 throw new RuntimeException(
                         "Conflict is of unknown type " + conflict.getConflictType() + ", which is not merge nor a crossing.");
             }
         }
 
         // No conflict vehicle triggered stopping
         return false;
 
     }
 
     /**
      * Approach a stop conflict. Currently this is equal to approaching a give-way conflict.
      * @param conflict conflict
      * @param leaders leaders
      * @param speed current speed
      * @param acceleration current acceleration
      * @param vehicleLength vehicle length
      * @param behavioralCharacteristics behavioral characteristics
      * @param speedLimitInfo speed limit info
      * @param carFollowingModel car-following model
      * @return whether to stop for this conflict
      * @throws ParameterException if a parameter is not defined
      */
     @SuppressWarnings("checkstyle:parameternumber")
     private static boolean stopForStopConflict(final HeadwayConflict conflict, final SortedSet<AbstractHeadwayGTU> leaders,
             final Speed speed, final Acceleration acceleration, final Length vehicleLength,
             final BehavioralCharacteristics behavioralCharacteristics, final SpeedLimitInfo speedLimitInfo,
             final CarFollowingModel carFollowingModel) throws ParameterException
     {
         return stopForGiveWayConflict(conflict, leaders, speed, acceleration, vehicleLength, behavioralCharacteristics,
                 speedLimitInfo, carFollowingModel);
     }
 
     /**
      * Approach an all-stop conflict.
      * @param conflict conflict to approach
      * @param conflictPlans set of plans for conflict
      * @return whether to stop for this conflict
      */
     private static boolean stopForAllStopConflict(final HeadwayConflict conflict, final ConflictPlans conflictPlans)
     {
         // TODO all-stop behavior
 
         if (conflictPlans.isStopPhaseRun(conflict.getStopLine()))
         {
             return false;
         }
 
         return false;
     }
 
     /**
      * Returns whether the conflicting link is on the route of the given gtu.
      * @param conflictingLink CrossSectionLink; conflicting link
      * @param gtu AbstractHeadwayGTU; gtu
      * @return whether the conflict is on the route of the given gtu
      */
     private static boolean isOnRoute(final CrossSectionLink conflictingLink, final AbstractHeadwayGTU gtu)
     {
         try
         {
             Route route = gtu.getRoute();
             if (route == null)
             {
                 // conservative assumption: it's on the route (gtu should be upstream of the conflict)
                 return true;
             }
             Node startNode = conflictingLink.getStartNode();
             Node endNode = conflictingLink.getEndNode();
             return route.contains(startNode) && route.contains(endNode)
                     && Math.abs(route.indexOf(endNode) - route.indexOf(startNode)) == 1;
         }
         catch (@SuppressWarnings("unused") UnsupportedOperationException uoe)
         {
             // conservative assumption: it's on the route (gtu should be upstream of the conflict)
             return true;
         }
     }
 
     /**
      * Returns a speed dependent distance needed behind the leader to completely pass the conflict.
      * @param speed speed
      * @param vehicleLength vehicle length
      * @param behavioralCharacteristics behavioral characteristics
      * @return speed dependent distance needed behind the leader to completely pass the conflict
      * @throws ParameterException if parameter is not available
      */
     private static Length passableDistance(final Speed speed, final Length vehicleLength,
             final BehavioralCharacteristics behavioralCharacteristics) throws ParameterException
     {
         return behavioralCharacteristics.getParameter(ParameterTypes.T).multiplyBy(speed)
                 .plus(behavioralCharacteristics.getParameter(ParameterTypes.S0)).plus(vehicleLength);
     }
 
     /**
      * Holds the tactical plans of a driver considering conflicts. These are remembered for consistency. For instance, if the
      * decision is made to yield as current deceleration suggests it's safe to do so, but the trajectory for stopping in front
      * of the conflict results in deceleration slightly above what is considered safe deceleration, the plan should not be
      * abandoned. Decelerations above what is considered safe deceleration may result due to numerical overshoot or other factor
      * coming into play in car-following models. Many other examples exist where a driver sticks to a certain plan.
      * <p>
      * Copyright (c) 2013-2016 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/current/license.html">OpenTrafficSim License</a>.
      * <p>
      * @version $Revision$, $LastChangedDate$, by $Author$, initial version Jun 7, 2016 <br>
      * @author <a href="http://www.tbm.tudelft.nl/averbraeck">Alexander Verbraeck</a>
      * @author <a href="http://www.tudelft.nl/pknoppers">Peter Knoppers</a>
      * @author <a href="http://www.transport.citg.tudelft.nl">Wouter Schakel</a>
      */
     public static final class ConflictPlans implements Serializable
     {
 
         /** */
         private static final long serialVersionUID = 20160811L;
 
         /** Set of current plans. */
         private final Map<String, String> yieldPlans = new HashMap<>();
 
         /** Set of conflicts that are still actively considered for a yield plan. */
         private final Set<String> activeYieldPlans = new HashSet<>();
 
         /** Phases of navigating an all-stop intersection per intersection. */
         private final HashMap<String, StopPhase> stopPhases = new HashMap<>();
 
         /** Estimated arrival times of vehicles at all-stop intersection. */
         private final HashMap<String, Time> arrivalTimes = new HashMap<>();
 
         /**
          * Returns whether a plan exists for yielding at the conflict for the given conflict GTU.
          * @param conflict conflict
          * @param gtu conflicting GTU
          * @return whether a plan exists for yielding at the conflict for the given conflict GTU
          */
         boolean isYieldPlan(final HeadwayConflict conflict, final AbstractHeadwayGTU gtu)
         {
             return this.yieldPlans.containsKey(conflict.getId()) && this.yieldPlans.get(conflict.getId()).equals(gtu.getId());
         }
 
         /**
          * Sets or maintains the plan to yield at the conflict for the given conflict RSU.
          * @param conflict conflict to yield at
          * @param gtu conflicting GTU
          */
         void setYieldPlan(final HeadwayConflict conflict, final AbstractHeadwayGTU gtu)
         {
             this.yieldPlans.put(conflict.getId(), gtu.getId());
             this.activeYieldPlans.add(conflict.getId());
         }
 
         /**
          * Clears any yield plan that was no longer kept active in the last evaluation of conflicts.
          */
         void cleanYieldPlans()
         {
             // remove any plan not represented in activePlans
             Iterator<String> iterator = this.yieldPlans.keySet().iterator();
             while (iterator.hasNext())
             {
                 String conflictId = iterator.next();
                 if (!this.activeYieldPlans.contains(conflictId))
                 {
                     iterator.remove();
                 }
             }
             // clear the activePlans for the next consideration of conflicts
             this.activeYieldPlans.clear();
         }
 
         /**
          * Sets the estimated arrival time of a GTU.
          * @param gtu GTU
          * @param time estimated arrival time
          */
         void setArrivalTime(final AbstractHeadwayGTU gtu, final Time time)
         {
             this.arrivalTimes.put(gtu.getId(), time);
         }
 
         /**
          * Returns the estimated arrival time of given GTU.
          * @param gtu GTU
          * @return estimated arrival time of given GTU
          */
         Time getArrivalTime(final AbstractHeadwayGTU gtu)
         {
             return this.arrivalTimes.get(gtu.getId());
         }
 
         /**
          * Sets the current phase to 'approach' for the given stop line.
          * @param stopLine stop line
          */
         void setStopPhaseApproach(final HeadwayStopLine stopLine)
         {
             this.stopPhases.put(stopLine.getId(), StopPhase.APPROACH);
         }
 
         /**
          * Sets the current phase to 'yield' for the given stop line.
          * @param stopLine stop line
          * @throws RuntimeException if the phase was not set to approach before
          */
         void setStopPhaseYield(final HeadwayStopLine stopLine)
         {
             Throw.when(
                     !this.stopPhases.containsKey(stopLine.getId())
                             || !this.stopPhases.get(stopLine.getId()).equals(StopPhase.APPROACH),
                     RuntimeException.class, "Yield stop phase is set for stop line that was not approached.");
             this.stopPhases.put(stopLine.getId(), StopPhase.YIELD);
         }
 
         /**
          * Sets the current phase to 'run' for the given stop line.
          * @param stopLine stop line
          * @throws RuntimeException if the phase was not set to approach before
          */
         void setStopPhaseRun(final HeadwayStopLine stopLine)
         {
             Throw.when(!this.stopPhases.containsKey(stopLine.getId()), RuntimeException.class,
                     "Run stop phase is set for stop line that was not approached.");
             this.stopPhases.put(stopLine.getId(), StopPhase.YIELD);
         }
 
         /**
          * @param stopLine stop line
          * @return whether the current phase is 'approach' for the given stop line
          */
         boolean isStopPhaseApproach(final HeadwayStopLine stopLine)
         {
             return this.stopPhases.containsKey(stopLine.getId())
                     && this.stopPhases.get(stopLine.getId()).equals(StopPhase.APPROACH);
         }
 
         /**
          * @param stopLine stop line
          * @return whether the current phase is 'yield' for the given stop line
          */
         boolean isStopPhaseYield(final HeadwayStopLine stopLine)
         {
             return this.stopPhases.containsKey(stopLine.getId())
                     && this.stopPhases.get(stopLine.getId()).equals(StopPhase.YIELD);
         }
 
         /**
          * @param stopLine stop line
          * @return whether the current phase is 'run' for the given stop line
          */
         boolean isStopPhaseRun(final HeadwayStopLine stopLine)
         {
             return this.stopPhases.containsKey(stopLine.getId()) && this.stopPhases.get(stopLine.getId()).equals(StopPhase.RUN);
         }
 
         /** {@inheritDoc} */
         @Override
         public String toString()
         {
             return "ConflictPlans";
         }
 
     }
 
     /**
      * Phases of navigating an all-stop intersection.
      * <p>
      * Copyright (c) 2013-2016 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/current/license.html">OpenTrafficSim License</a>.
      * <p>
      * @version $Revision$, $LastChangedDate$, by $Author$, initial version Jun 30, 2016 <br>
      * @author <a href="http://www.tbm.tudelft.nl/averbraeck">Alexander Verbraeck</a>
      * @author <a href="http://www.tudelft.nl/pknoppers">Peter Knoppers</a>
      * @author <a href="http://www.transport.citg.tudelft.nl">Wouter Schakel</a>
      */
     private enum StopPhase
     {
         /** Approaching stop intersection. */
         APPROACH,
 
         /** Yielding for stop intersection. */
         YIELD,
 
         /** Running over stop intersection. */
         RUN;
     }
 
 }