Class CarFollowingUtil


  • public final class CarFollowingUtil
    extends Object
    Static methods regarding car-following for composition in tactical planners.

    Copyright (c) 2013-2020 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 23, 2016
    Author:
    Alexander Verbraeck, Wouter Schakel
    • Method Detail

      • followSingleLeader

        public static Acceleration followSingleLeader​(CarFollowingModel carFollowingModel,
                                                      Parameters parameters,
                                                      Speed speed,
                                                      SpeedLimitInfo speedLimitInfo,
                                                      Length distance,
                                                      Speed leaderSpeed)
                                               throws ParameterException
        Follow a set of headway GTUs.
        Parameters:
        carFollowingModel - CarFollowingModel; car-following model
        parameters - Parameters; parameters
        speed - Speed; current speed
        speedLimitInfo - SpeedLimitInfo; speed limit info
        distance - Length; distance
        leaderSpeed - Speed; speed of the leader
        Returns:
        acceleration for following the leader
        Throws:
        ParameterException - if a parameter is not given or out of bounds
      • followSingleLeader

        public static Acceleration followSingleLeader​(CarFollowingModel carFollowingModel,
                                                      Parameters parameters,
                                                      Speed speed,
                                                      SpeedLimitInfo speedLimitInfo,
                                                      HeadwayGTU leader)
                                               throws ParameterException
        Follow a set of headway GTUs.
        Parameters:
        carFollowingModel - CarFollowingModel; car-following model
        parameters - Parameters; parameters
        speed - Speed; current speed
        speedLimitInfo - SpeedLimitInfo; speed limit info
        leader - HeadwayGTU; leader
        Returns:
        acceleration for following the leader
        Throws:
        ParameterException - if a parameter is not given or out of bounds
      • stop

        public static Acceleration stop​(CarFollowingModel carFollowingModel,
                                        Parameters parameters,
                                        Speed speed,
                                        SpeedLimitInfo speedLimitInfo,
                                        Length distance)
                                 throws ParameterException
        Stop within given distance.
        Parameters:
        carFollowingModel - CarFollowingModel; car-following model
        parameters - Parameters; parameters
        speed - Speed; current speed
        speedLimitInfo - SpeedLimitInfo; speed limit info
        distance - Length; distance to stop over
        Returns:
        acceleration to stop over distance
        Throws:
        ParameterException - if a parameter is not given or out of bounds
      • constantAccelerationStop

        public static Acceleration constantAccelerationStop​(CarFollowingModel carFollowingModel,
                                                            Parameters parameters,
                                                            Speed speed,
                                                            Length distance)
                                                     throws ParameterException
        Return constant acceleration in order to stop in specified distance. The car-following model is used to determine the stopping distance (i.e. distance remaining at stand still, e.g. 1-3m).
        Parameters:
        carFollowingModel - CarFollowingModel; car-following model
        parameters - Parameters; parameters
        speed - Speed; current speed
        distance - Length; distance to stop over
        Returns:
        constant acceleration in order to stop in specified distance
        Throws:
        ParameterException - on missing parameter
      • freeAcceleration

        public static Acceleration freeAcceleration​(CarFollowingModel carFollowingModel,
                                                    Parameters parameters,
                                                    Speed speed,
                                                    SpeedLimitInfo speedLimitInfo)
                                             throws ParameterException
        Calculate free acceleration.
        Parameters:
        carFollowingModel - CarFollowingModel; car-following model
        parameters - Parameters; parameters
        speed - Speed; current speed
        speedLimitInfo - SpeedLimitInfo; speed limit info
        Returns:
        acceleration free acceleration
        Throws:
        ParameterException - if a parameter is not given or out of bounds
      • approachTargetSpeed

        public static Acceleration approachTargetSpeed​(CarFollowingModel carFollowingModel,
                                                       Parameters parameters,
                                                       Speed speed,
                                                       SpeedLimitInfo speedLimitInfo,
                                                       Length distance,
                                                       Speed targetSpeed)
                                                throws 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 - CarFollowingModel; car-following model to use
        parameters - Parameters; parameters
        speed - Speed; current speed
        speedLimitInfo - SpeedLimitInfo; info regarding the desired speed for car-following
        distance - Length; distance to the location of the target speed
        targetSpeed - Speed; target speed
        Returns:
        acceleration acceleration based on the car-following model in order to adjust the speed
        Throws:
        ParameterException - if parameter exception occurs
        NullPointerException - if any input is null
        IllegalArgumentException - if the distance or target speed is not at least 0