org.opentrafficsim.road.gtu.lane.tactical.util

Class SpeedLimitUtil

java.lang.Object

org.opentrafficsim.road.gtu.lane.tactical.util.SpeedLimitUtil

public final class SpeedLimitUtil
extends Object

Static methods regarding speed limits for composition in tactical planners.

Copyright (c) 2013-2016 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved.
BSD-style license. See OpenTrafficSim License.

Version:

$Revision$, $LastChangedDate$, by $Author$, initial version May 20, 2016

Author:

Alexander Verbraeck, Peter Knoppers, Wouter Schakel

Field Summary

Fields

Modifier and Type	Field and Description
static org.opentrafficsim.core.gtu.behavioralcharacteristics.ParameterTypeAcceleration	A_LAT Maximum comfortable acceleration in the lateral direction.

Method Summary

Modifier and Type	Method and Description
static org.djunits.value.vdouble.scalar.Acceleration	approachTargetSpeed(CarFollowingModel carFollowingModel, org.opentrafficsim.core.gtu.behavioralcharacteristics.BehavioralCharacteristics behavioralCharacteristics, org.djunits.value.vdouble.scalar.Speed speed, SpeedLimitInfo speedLimitInfo, org.djunits.value.vdouble.scalar.Length distance, org.djunits.value.vdouble.scalar.Speed targetSpeed) Returns an acceleration based on the car-following model in order to adjust the speed to a given value at some location ahead.
static org.djunits.value.vdouble.scalar.Acceleration	considerSpeedLimitTransitions(org.opentrafficsim.core.gtu.behavioralcharacteristics.BehavioralCharacteristics behavioralCharacteristics, org.djunits.value.vdouble.scalar.Speed speed, SpeedLimitProspect speedLimitProspect, CarFollowingModel carFollowingModel) Acceleration for speed limit transitions.
static org.djunits.value.vdouble.scalar.Speed	getLegalSpeedLimit(SpeedLimitInfo speedLimitInfo) Returns the minimum speed of the applicable speed limit types MAX_LEGAL_VEHICLE_SPEED, ROAD_CLASS, FIXED_SIGN and DYNAMIC_SIGN.
static org.djunits.value.vdouble.scalar.Speed	getMaximumVehicleSpeed(SpeedLimitInfo speedLimitInfo) Returns the speed of speed limit type MAX_VEHICLE_SPEED.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

A_LAT

public static final org.opentrafficsim.core.gtu.behavioralcharacteristics.ParameterTypeAcceleration A_LAT

Maximum comfortable acceleration in the lateral direction.

Method Detail

getLegalSpeedLimit

public static org.djunits.value.vdouble.scalar.Speed getLegalSpeedLimit(SpeedLimitInfo speedLimitInfo)

Returns the minimum speed of the applicable speed limit types MAX_LEGAL_VEHICLE_SPEED, ROAD_CLASS, FIXED_SIGN and DYNAMIC_SIGN. ROAD_CLASS is only used if FIXED_SIGN and DYNAMIC_SIGN are not present. This method may be overridden by subclasses to implement additional behavior regarding legal speed limits.

Parameters:

speedLimitInfo - speed limit info

Returns:

minimum of speed of speed limit types

Throws:

NullPointerException - if speed limit info is null

getMaximumVehicleSpeed

public static org.djunits.value.vdouble.scalar.Speed getMaximumVehicleSpeed(SpeedLimitInfo speedLimitInfo)

Returns the speed of speed limit type MAX_VEHICLE_SPEED. This method may be overridden by subclasses to implement additional behavior regarding maximum vehicle speed limits.

Parameters:

speedLimitInfo - speed limit info

Returns:

speed of speed limit type MAX_VEHICLE_SPEED

Throws:

NullPointerException - if speed limit info is null

considerSpeedLimitTransitions

public static org.djunits.value.vdouble.scalar.Acceleration considerSpeedLimitTransitions(org.opentrafficsim.core.gtu.behavioralcharacteristics.BehavioralCharacteristics behavioralCharacteristics,
                                                                                          org.djunits.value.vdouble.scalar.Speed speed,
                                                                                          SpeedLimitProspect speedLimitProspect,
                                                                                          CarFollowingModel carFollowingModel)
                                                                                   throws org.opentrafficsim.core.gtu.behavioralcharacteristics.ParameterException

Acceleration for speed limit transitions. This implementation decelerates before curves and speed bumps. For this it uses approachTargetSpeed() of the abstract car-following model implementation. All remaining transitions happen in the default manner, i.e. deceleration and acceleration after the speed limit change and governed by the car-following model.

Parameters:

behavioralCharacteristics - behavioral characteristics

speed - current speed

speedLimitProspect - speed limit prospect

carFollowingModel - car following model

Returns:

acceleration for speed limit transitions

Throws:

org.opentrafficsim.core.gtu.behavioralcharacteristics.ParameterException - if a required parameter is not found

approachTargetSpeed

public static org.djunits.value.vdouble.scalar.Acceleration approachTargetSpeed(CarFollowingModel carFollowingModel,
                                                                                org.opentrafficsim.core.gtu.behavioralcharacteristics.BehavioralCharacteristics behavioralCharacteristics,
                                                                                org.djunits.value.vdouble.scalar.Speed speed,
                                                                                SpeedLimitInfo speedLimitInfo,
                                                                                org.djunits.value.vdouble.scalar.Length distance,
                                                                                org.djunits.value.vdouble.scalar.Speed targetSpeed)
                                                                         throws org.opentrafficsim.core.gtu.behavioralcharacteristics.ParameterException

Returns an acceleration based on the car-following model in order to adjust the speed to a given value at some location ahead. This is done by placing a virtual vehicle somewhere near the location. Both the location and speed of this virtual vehicle are dynamically adjusted to resemble a car-following situation. To explain, first consider the situation where a virtual vehicle is placed at the target speed and such that the equilibrium headway is in line with the location:

 
  ___    location of target speed --)|        ___
 |___|(--------------s--------------) (--h--)|___| ))) vTar
 

Here, s is the distance to the target speed, and h is the desired headway if the vehicle would drive at the target speed vTar.

In this way car-following models will first underestimate the required deceleration, as the virtual vehicle is actually stationary and does not move with vTar at all. Because of this underestimation, strong deceleration is required later. This behavior is not in line with the sensitivity parameters of the car-following model.

To correct for the fact that the virtual vehicle is actually not moving, the speed difference should be larger, i.e. the speed of the virtual vehicle vTar' should be lower. We require:

• if v = vTar then vTar' = vTar, otherwise there is an incentive to accelerate or decelerate for no good reason
• if vTar ~ 0 then vTar' ~ 0, as car-following models are suitable for stopping and need no additional incentive to decelerate in such cases
• if 0 < vTar < v then vTar' < vTar, introducing additional deceleration to compensate for the fact that the virtual vehicle does not move

These requirements are met by vTar' = vTar * (vTar/v) = vTar^2/v.

Furthermore, if v < vTar we get vTar' > vTar leading to additional acceleration. Acceleration is then appropriate, and possibly limited by a free term in the car-following model.

The virtual vehicle is thus placed with speed vTar' at a distance s + h' where h' is the desired headway if the vehicle would drive at speed vTar'. Both vTar' and h' depend on the current speed of the vehicle, so the virtual vehicle in this case actually moves, but not with vTar.

This approach has been tested with the IDM+ to deliver decelerations in line with the parameters. On a plane with initial speed ranging from 0 to 33.33m/s and a target speed in 300m also ranging from 0 to 33.33m/s, strongest deceleration is equal to the car-following model stopping from 33.33m/s to a stand-still vehicle in 300m (+ stopping distance of 3m). Throughout the plane the maximum deceleration of each scenario is close to this value, unless the initial speed is so low, and the target speed is so high, that such levels of deceleration are never required.

Parameters:

carFollowingModel - car-following model to use

behavioralCharacteristics - behavioral characteristics

speed - current speed

speedLimitInfo - info regarding the desired speed for car-following

distance - distance to the location of the target speed

targetSpeed - target speed

Returns:

acceleration acceleration based on the car-following model in order to adjust the speed

Throws:

org.opentrafficsim.core.gtu.behavioralcharacteristics.ParameterException - if parameter exception occurs

NullPointerException - if any input is null

IllegalArgumentException - if the distance or target speed is not at least 0