SUMO - Simulation of Urban MObility
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MSCFModel_Krauss.cpp
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1 /****************************************************************************/
11 // Krauss car-following model, with acceleration decrease and faster start
12 /****************************************************************************/
13 // SUMO, Simulation of Urban MObility; see http://sumo.sourceforge.net/
14 // Copyright (C) 2001-2013 DLR (http://www.dlr.de/) and contributors
15 /****************************************************************************/
16 //
17 // This file is part of SUMO.
18 // SUMO is free software: you can redistribute it and/or modify
19 // it under the terms of the GNU General Public License as published by
20 // the Free Software Foundation, either version 3 of the License, or
21 // (at your option) any later version.
22 //
23 /****************************************************************************/
24 
25 
26 // ===========================================================================
27 // included modules
28 // ===========================================================================
29 #ifdef _MSC_VER
30 #include <windows_config.h>
31 #else
32 #include <config.h>
33 #endif
34 
35 #include <microsim/MSVehicle.h>
36 #include <microsim/MSLane.h>
37 #include "MSCFModel_Krauss.h"
40 
41 
42 // ===========================================================================
43 // method definitions
44 // ===========================================================================
46  SUMOReal dawdle, SUMOReal headwayTime)
47  : MSCFModel_KraussOrig1(vtype, accel, decel, dawdle, headwayTime) {
48 }
49 
50 
52 
53 
55 MSCFModel_Krauss::followSpeed(const MSVehicle* const veh, SUMOReal speed, SUMOReal gap, SUMOReal predSpeed, SUMOReal predMaxDecel) const {
56  return MIN2(_vsafe(gap, predSpeed, predMaxDecel), maxNextSpeed(speed, veh));
57 }
58 
59 
61 MSCFModel_Krauss::stopSpeed(const MSVehicle* const veh, SUMOReal gap) const {
62  return MIN2(_vsafe(gap, 0, 0), maxNextSpeed(veh->getSpeed(), veh));
63 }
64 
65 
68  // generate random number out of [0,1]
69  SUMOReal random = RandHelper::rand();
70  // Dawdle.
71  if (speed < myAccel) {
72  // we should not prevent vehicles from driving just due to dawdling
73  // if someone is starting, he should definitely start
74  // (but what about slow-to-start?)!!!
75  speed -= ACCEL2SPEED(myDawdle * speed * random);
76  } else {
77  speed -= ACCEL2SPEED(myDawdle * myAccel * random);
78  }
79  return MAX2(SUMOReal(0), speed);
80 }
81 
82 
85 MSCFModel_Krauss::_vsafe(SUMOReal gap, SUMOReal predSpeed, SUMOReal predMaxDecel) const {
86  if (predSpeed < predMaxDecel) {
87  // avoid discretization error at low speeds
88  predSpeed = 0;
89  }
90  if (predSpeed == 0) {
91  if (gap < 0.01) {
92  return 0;
93  }
94  return (SUMOReal)(-myTauDecel + sqrt(myTauDecel * myTauDecel + 2. * myDecel * gap));
95  }
96  // follow the leader
97  // g=gap, t=myHeadwayTime, a=predMaxDecel, b=myDecel, v=predSpeed, x=vSafe
98  // Solution approach: equal distances after leader and follower have stopped (partly discretized).
99  // g + (v^2 - a*v)/(2*a) = x*t + (x^2 - b*x)/(2*b) + 0.5
100  // The term (+ 0.5) gives an upper bound for the follower stopping distance to handle discretization errors.
101  // Unfortunately, the solution approach is not correct when b > a since the
102  // follower path may cross the leader path even with equal stopping distances.
103  // As a workaround we lower the value of b to get a collision free model
104  // This approach should be refined to get a higher (still safe) following speed.
105  const SUMOReal egoDecel = MIN2(myDecel, predMaxDecel);
106  return (SUMOReal)(0.5 * sqrt(
107  4.0 * egoDecel * (2.0 * gap + predSpeed * predSpeed / predMaxDecel - predSpeed - 1.0)
108  + (egoDecel * (2.0 * myHeadwayTime - 1.0))
109  * (egoDecel * (2.0 * myHeadwayTime - 1.0)))
110  + myDecel * (0.5 - myHeadwayTime));
111 }
112 
113 
114 MSCFModel*
116  return new MSCFModel_Krauss(vtype, myAccel, myDecel, myDawdle, myHeadwayTime);
117 }
118 
119 
120 //void MSCFModel::saveState(std::ostream &os) {}
121