1 package org.opentrafficsim.core.gtu.following;
2
3 import org.opentrafficsim.core.unit.AccelerationUnit;
4 import org.opentrafficsim.core.unit.LengthUnit;
5 import org.opentrafficsim.core.unit.SpeedUnit;
6 import org.opentrafficsim.core.unit.TimeUnit;
7 import org.opentrafficsim.core.value.conversions.Calc;
8 import org.opentrafficsim.core.value.vdouble.scalar.DoubleScalar;
9 import org.opentrafficsim.core.value.vdouble.scalar.MutableDoubleScalar;
10
11 /**
12 * IDMPlus implements the <i>Integrated Lane Change Model with Relaxation and Synchronization</i> as published by Wouter
13 * J. Schakel, Bart van Arem, Member, IEEE, and Bart D. Netten. 2012. <br>
14 * There are two nasty type setting errors in equation 7 in this published version of the paper. Both times an equals
15 * sign (<cite>=</cite>) after <cite>a<sub>gain</sub></cite> should <b>not</b> be there.
16 * <p>
17 * Copyright (c) 2013-2014 Delft University of Technology, PO Box 5, 2600 AA, Delft, the Netherlands. All rights
18 * reserved. <br>
19 * BSD-style license. See <a href="http://opentrafficsim.org/node/13">OpenTrafficSim License</a>.
20 * <p>
21 * @version Jul 4, 2014 <br>
22 * @author <a href="http://www.tudelft.nl/pknoppers">Peter Knoppers</a>
23 */
24 public class IDMPlus extends AbstractGTUFollowingModel
25 {
26 /** Preferred net longitudinal distance when stopped [m]. */
27 private final DoubleScalar.Rel<LengthUnit> s0;
28
29 /** Longitudinal acceleration [m/s^2]. */
30 private final DoubleScalar.Abs<AccelerationUnit> a;
31
32 /** Longitudinal deceleration [m/s^2]. (Should be a positive value even though it is a <b>de</b>celeration.) */
33 private final DoubleScalar.Abs<AccelerationUnit> b;
34
35 /** Safe time headway. */
36 private final DoubleScalar.Rel<TimeUnit> tSafe;
37
38 /**
39 * Mean speed limit adherence (1.0: mean free speed equals the speed limit; 1.1: mean free speed equals 110% of the
40 * speed limit, etc.).
41 */
42 private final double delta;
43
44 /**
45 * Time slot size used by IDMPlus by (not defined in the paper, but 0.5s is a reasonable trade-off between
46 * computational speed and accuracy).
47 */
48 private final DoubleScalar.Rel<TimeUnit> stepSize = new DoubleScalar.Rel<TimeUnit>(0.5, TimeUnit.SECOND);
49
50 /**
51 * Construct a new IDM+ car following model with reasonable values (reasonable for passenger cars). <br>
52 * These values are from <b>Integrated Lane Change Model with Relaxation and Synchronization</b> by Wouter J.
53 * Schakel, Victor L. Knoop, and Bart van Arem, published in Transportation Research Record: Journal of the
54 * Transportation Research Board, No. 2316, Transportation Research Board of the National Academies, Washington,
55 * D.C., 2012, pp. 47–57.
56 */
57 public IDMPlus()
58 {
59 this.a = new DoubleScalar.Abs<AccelerationUnit>(1.56, AccelerationUnit.METER_PER_SECOND_2);
60 this.b = new DoubleScalar.Abs<AccelerationUnit>(2.09, AccelerationUnit.METER_PER_SECOND_2);
61 this.s0 = new DoubleScalar.Rel<LengthUnit>(3, LengthUnit.METER);
62 this.tSafe = new DoubleScalar.Rel<TimeUnit>(1.2, TimeUnit.SECOND);
63 this.delta = 1d;
64 }
65
66 /**
67 * Construct a new IDMPlus car following model.
68 * @param a DoubleScalar.Abs<AccelerationUnit>; the maximum acceleration of a stationary vehicle (normal value
69 * is 1 m/s/s)
70 * @param b DoubleScalar.Abs<AccelerationUnit>; the maximum deemed-safe deceleration (this is a positive
71 * value)
72 * @param s0 DoubleScalar.Rel<LengthUnit>; the minimum stationary headway
73 * @param tSafe DoubleScalar.Rel<TimeUnit>; the minimum time-headway
74 * @param delta double; the speed limit adherence (1.0; mean free speed equals the speed limit; 1.1: mean free speed
75 * equals 110% of the speed limit; etc.)
76 */
77 public IDMPlus(final DoubleScalar.Abs<AccelerationUnit> a, final DoubleScalar.Abs<AccelerationUnit> b,
78 final DoubleScalar.Rel<LengthUnit> s0, final DoubleScalar.Rel<TimeUnit> tSafe, final double delta)
79 {
80 this.a = a;
81 this.b = b;
82 this.s0 = s0;
83 this.tSafe = tSafe;
84 this.delta = delta;
85 }
86
87 /**
88 * Desired speed (taking into account the urge to drive a little faster or slower than the posted speed limit).
89 * @param speedLimit DoubleScalarAbs<SpeedUnit>; the speed limit
90 * @param followerMaximumSpeed DoubleScalar.Abs<SpeedUnit>; the maximum speed that the follower can drive
91 * @return DoubleScalarRel<SpeedUnit>; the desired speed
92 */
93 private DoubleScalar.Rel<SpeedUnit> vDes(final DoubleScalar.Abs<SpeedUnit> speedLimit,
94 final DoubleScalar.Abs<SpeedUnit> followerMaximumSpeed)
95 {
96 return new DoubleScalar.Rel<SpeedUnit>(Math.min(this.delta * speedLimit.getSI(), followerMaximumSpeed.getSI()),
97 SpeedUnit.METER_PER_SECOND);
98 }
99
100 /** {@inheritDoc} */
101 public final DoubleScalar.Abs<AccelerationUnit> computeAcceleration(
102 final DoubleScalar.Abs<SpeedUnit> followerSpeed, final DoubleScalar.Abs<SpeedUnit> followerMaximumSpeed,
103 final DoubleScalar.Abs<SpeedUnit> leaderSpeed, final DoubleScalar.Rel<LengthUnit> headway,
104 final DoubleScalar.Abs<SpeedUnit> speedLimit)
105 {
106 double leftComponent = 1 - Math.pow(followerSpeed.getSI() / vDes(speedLimit, followerMaximumSpeed).getSI(), 4);
107 if (Double.isNaN(leftComponent))
108 {
109 leftComponent = 0;
110 }
111 // if (leftComponent < 0)
112 // {
113 // System.out.println("leftComponent is " + leftComponent);
114 // }
115 MutableDoubleScalar.Rel<AccelerationUnit> logWeightedAccelerationTimes2 =
116 new MutableDoubleScalar.Rel<AccelerationUnit>(Math.sqrt(this.a.getSI() * this.b.getSI()),
117 AccelerationUnit.METER_PER_SECOND_2);
118 logWeightedAccelerationTimes2.multiply(2); // don't forget the times 2
119
120 DoubleScalar.Rel<SpeedUnit> dV = DoubleScalar.minus(followerSpeed, leaderSpeed).immutable();
121 // System.out.println("dV is " + dV);
122 // System.out.println(" v is " + gtu.speed(thisEvaluationTime));
123 // System.out.println("s0 is " + this.s0);
124 DoubleScalar.Rel<LengthUnit> sStar =
125 DoubleScalar.plus(
126 DoubleScalar.plus(this.s0, Calc.speedTimesTime(followerSpeed, this.tSafe)).immutable(),
127 Calc.speedTimesTime(
128 dV,
129 Calc.speedDividedByAcceleration(followerSpeed,
130 logWeightedAccelerationTimes2.immutable()))).immutable();
131 if (sStar.getSI() < 0)
132 {
133 // Negative value should be treated as 0? This is NOT in the LMRS paper
134 // Without this "fix" a higher speed of the leader may cause a lower acceleration (which is crazy)
135 sStar = new DoubleScalar.Rel<LengthUnit>(0, LengthUnit.METER);
136 }
137 // System.out.println("s* is " + sStar);
138
139 double rightComponent = 1 - Math.pow(sStar.getSI() / headway.getSI(), 2);
140 // if (rightComponent < 0)
141 // {
142 // System.out.println("rightComponent is " + rightComponent);
143 // }
144 MutableDoubleScalar.Abs<AccelerationUnit> newAcceleration =
145 new MutableDoubleScalar.Abs<AccelerationUnit>(this.a);
146 newAcceleration.multiply(Math.min(leftComponent, rightComponent));
147 // System.out.println("newAcceleration is " + newAcceleration);
148 if (newAcceleration.getSI() * this.stepSize.getSI() + followerSpeed.getSI() < 0)
149 {
150 // System.out.println("Preventing follower from driving backwards " + follower);
151 newAcceleration =
152 new MutableDoubleScalar.Abs<AccelerationUnit>(-followerSpeed.getSI() / this.stepSize.getSI(),
153 AccelerationUnit.METER_PER_SECOND_2);
154 }
155 // System.out.println("newAcceleration is " + newAcceleration);
156 return newAcceleration.immutable();
157 }
158
159 /** {@inheritDoc} */
160 @Override
161 public final DoubleScalar.Rel<TimeUnit> getStepSize()
162 {
163 return new DoubleScalar.Rel<TimeUnit>(this.stepSize);
164 }
165
166 /** {@inheritDoc} */
167 @Override
168 public final DoubleScalar.Abs<AccelerationUnit> maximumSafeDeceleration()
169 {
170 return this.b;
171 }
172
173 /** {@inheritDoc} */
174 @Override
175 public final String getName()
176 {
177 return "IDM+";
178 }
179
180 /** {@inheritDoc} */
181 @Override
182 public final String getLongName()
183 {
184 return String.format("%s (a=%.1fm/s\u00b2, b=%.1fm/s\u00b2, s0=%.1fm, tSafe=%.1fs, delta=%.2f)", getName(),
185 this.a.getSI(), this.b.getSI(), this.s0.getSI(), this.tSafe.getSI(), this.delta);
186 }
187
188 }