* Copyright (c) 2013-2015 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights reserved.
* BSD-style license. See OpenTrafficSim License.
*
* @version $Revision: 1408 $, $LastChangedDate: 2015-09-24 15:17:25 +0200 (Thu, 24 Sep 2015) $, by $Author: pknoppers $,
* initial version Jul 4, 2014
* @author Peter Knoppers
*/
public class IDMPlus extends AbstractGTUFollowingModel
{
/** Preferred net longitudinal distance when stopped [m]. */
private final Length.Rel s0;
/** Longitudinal acceleration [m/s^2]. */
private final Acceleration a;
/** Longitudinal deceleration [m/s^2]. (Should be a positive value even though it is a deceleration.) */
private final Acceleration b;
/** Safe time headway. */
private final Time.Rel tSafe;
/**
* Mean speed limit adherence (1.0: mean free speed equals the speed limit; 1.1: mean free speed equals 110% of the speed
* limit, etc.).
*/
private final double delta;
/**
* Time slot size used by IDMPlus by (not defined in the paper, but 0.5s is a reasonable trade-off between computational
* speed and accuracy).
*/
private final Time.Rel stepSize = new Time.Rel(0.5, TimeUnit.SECOND);
/**
* Construct a new IDM+ car following model with reasonable values (reasonable for passenger cars).
* These values are from Integrated Lane Change Model with Relaxation and Synchronization by Wouter J. Schakel,
* Victor L. Knoop, and Bart van Arem, published in Transportation Research Record: Journal of the Transportation Research
* Board, No. 2316, Transportation Research Board of the National Academies, Washington, D.C., 2012, pp. 47–57.
*/
public IDMPlus()
{
this.a = new Acceleration(1.56, AccelerationUnit.METER_PER_SECOND_2);
this.b = new Acceleration(2.09, AccelerationUnit.METER_PER_SECOND_2);
this.s0 = new Length.Rel(3, LengthUnit.METER);
this.tSafe = new Time.Rel(1.2, TimeUnit.SECOND);
this.delta = 1d;
}
/**
* Construct a new IDMPlus car following model.
* @param a DoubleScalar.Abs<AccelerationUnit>; the maximum acceleration of a stationary vehicle (normal value is 1
* m/s/s)
* @param b DoubleScalar.Abs<AccelerationUnit>; the maximum deemed-safe deceleration (this is a positive value)
* @param s0 DoubleScalar.Rel<LengthUnit>; the minimum stationary headway
* @param tSafe DoubleScalar.Rel<TimeUnit>; the minimum time-headway
* @param delta double; the speed limit adherence (1.0; mean free speed equals the speed limit; 1.1: mean free speed equals
* 110% of the speed limit; etc.)
*/
public IDMPlus(final Acceleration a, final Acceleration b, final Length.Rel s0, final Time.Rel tSafe,
final double delta)
{
this.a = a;
this.b = b;
this.s0 = s0;
this.tSafe = tSafe;
this.delta = delta;
}
/**
* Desired speed (taking into account the urge to drive a little faster or slower than the posted speed limit).
* @param speedLimit DoubleScalarAbs<SpeedUnit>; the speed limit
* @param followerMaximumSpeed DoubleScalar.Abs<SpeedUnit>; the maximum speed that the follower can drive
* @return DoubleScalarRel<SpeedUnit>; the desired speed
*/
private Speed vDes(final Speed speedLimit, final Speed followerMaximumSpeed)
{
return new Speed(Math.min(this.delta * speedLimit.getSI(), followerMaximumSpeed.getSI()), SpeedUnit.SI);
}
/** {@inheritDoc} */
public final Acceleration computeAcceleration(final Speed followerSpeed, final Speed followerMaximumSpeed,
final Speed leaderSpeed, final Length.Rel headway, final Speed speedLimit)
{
double leftComponent = 1 - Math.pow(followerSpeed.getSI() / vDes(speedLimit, followerMaximumSpeed).getSI(), 4);
if (Double.isNaN(leftComponent))
{
leftComponent = 0;
}
// if (leftComponent < 0)
// {
// System.out.println("leftComponent is " + leftComponent);
// }
Acceleration logWeightedAccelerationTimes2 =
new Acceleration(Math.sqrt(this.a.getSI() * this.b.getSI()), AccelerationUnit.SI).multiplyBy(2);
// don't forget the times 2
Speed dV = followerSpeed.minus(leaderSpeed);
// System.out.println("dV is " + dV);
// System.out.println(" v is " + gtu.speed(thisEvaluationTime));
// System.out.println("s0 is " + this.s0);
Length.Rel sStar =
this.s0.plus(followerSpeed.multiplyBy(this.tSafe)).plus(
dV.multiplyBy(followerSpeed.divideBy(logWeightedAccelerationTimes2)));
/*-
this.s0.plus(Calc.speedTimesTime(followerSpeed, this.tSafe)).plus(
Calc.speedTimesTime(dV, Calc.speedDividedByAcceleration(followerSpeed, logWeightedAccelerationTimes2)));
*/
if (sStar.getSI() < 0)
{
// Negative value should be treated as 0? This is NOT in the LMRS paper
// Without this "fix" a higher speed of the leader may cause a lower acceleration (which is crazy)
sStar = new Length.Rel(0, LengthUnit.SI);
}
// System.out.println("s* is " + sStar);
double rightComponent = 1 - Math.pow(sStar.getSI() / headway.getSI(), 2);
// if (rightComponent < 0)
// {
// System.out.println("rightComponent is " + rightComponent);
// }
Acceleration newAcceleration = new Acceleration(this.a).multiplyBy(Math.min(leftComponent, rightComponent));
// System.out.println("newAcceleration is " + newAcceleration);
if (newAcceleration.getSI() * this.stepSize.getSI() + followerSpeed.getSI() < 0)
{
// System.out.println("Preventing follower from driving backwards " + follower);
newAcceleration = new Acceleration(-followerSpeed.getSI() / this.stepSize.getSI(), AccelerationUnit.SI);
}
// System.out.println("newAcceleration is " + newAcceleration);
return newAcceleration;
}
/** {@inheritDoc} */
@Override
public final Time.Rel getStepSize()
{
return new Time.Rel(this.stepSize);
}
/** {@inheritDoc} */
@Override
public final Acceleration maximumSafeDeceleration()
{
return this.b;
}
/** {@inheritDoc} */
@Override
public final String getName()
{
return "IDM+";
}
/** {@inheritDoc} */
@Override
public final String getLongName()
{
return String.format("%s (a=%.1fm/s\u00b2, b=%.1fm/s\u00b2, s0=%.1fm, tSafe=%.1fs, delta=%.2f)", getName(),
this.a.getSI(), this.b.getSI(), this.s0.getSI(), this.tSafe.getSI(), this.delta);
}
}