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Publication Number: FHWA-HRT-08-051
Date: June 2008

Surrogate Safety Assessment Model and Validation: Final Report

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Appendix B. Abrupt Lane-Change Behavior

This section provides an example of the abrupt lane-changing behavior experienced in VISSIM using version 4.1. Figure 243 shows two vehicles stopped at the red light on the eastbound approach to the intersection, with two more vehicles approaching. The first vehicle is the approaching vehicle that is closer to the downstream stop line, while the second vehicle is the furthest from the stop line.

Figure 243. Screen Capture. First and Second Vehicles Arriving. This is a screen capture from a running VISSIM simulation. Two vehicles stop at the red light on the eastbound approach, with two more vehicles arriving after each other.

Figure 243. Screen Capture. First and Second Vehicles Arriving.

In figure 244, the first vehicle has come to a complete stop, while the second vehicle has decided to change lanes and queue up on the outer left lane of the eastbound approach.

Figure 244. Screen Capture. First Vehicle Stops and Second Vehicle Decides to Change Lane. This is a screen capture from a running VISSIM simulation. Two vehicles stop at the red light on the eastbound approach, with two more vehicles (referred to as the first vehicle and the second vehicle) arriving after each other. The first vehicle has come to a complete stop, while the second vehicle has decided to change lanes and queue up on the outer left lane of the eastbound approach.

Figure 244. Screen Capture. First Vehicle Stops and Second Vehicle Decides to Change Lanes.

In figure 245, the second vehicle changes lanes and stops diagonally.

Figure 245. Screen Capture. Second Vehicle Changes Lanes and Stops. This is a screen capture from a running VISSIM simulation. Two vehicles stop at the red light on the eastbound approach, with two more vehicles (referred to as the first vehicle and the second vehicle) stop behind. The first vehicle has come to a complete stop, while the second vehicle changes lanes and stops diagonally.

Figure 245. Screen Capture. Second Vehicle Changes Lanes and Stops.

In figure 246, a third vehicle is approaching the intersection, also traveling eastbound.

Figure 246. Screen Capture. Third Vehicle Arriving. This is a screen capture from a running VISSIM simulation. Two vehicles stop at the red light on the eastbound approach, with two more vehicles (referred to as the first vehicle, the second vehicle, and the third vehicle) stop behind. The first vehicle has come to a complete stop, while the second vehicle has changed lanes and stopped diagonally. A third vehicle is arriving at the eastbound intersection.

Figure 246. Screen Capture. Third Vehicle Arriving.

As shown in figure 247, the third vehicle fails to recognize the presence of the second vehicle (only partially in the lane) and passes right through it. In occupying the same physical location at the same time, SSAM regards this event as a crash (i.e., as a conflict event with a minimum TTC of 0 seconds). This behavior was observed in VISSIM 4.1 and in all other simulation systems. However, this represents a problematic issue in the field validation effort, correlating simulated conflicts to actual crash data.

Figure 247. Screen Capture. Third Vehicle Crashing into Second Vehicle. This is a screen capture from a running VISSIM simulation. Two vehicles stop at the red light on the eastbound approach, with three more vehicles (referred to as the first vehicle, the second vehicle, and the third vehicle) stop behind. The first vehicle has come to a complete stop, while the second vehicle has changed lanes and stopped diagonally. The third vehicle fails to recognize the presence of the second vehicle and crashes.

Figure 247. Screen Capture. Third Vehicle Crashing into Second Vehicle.

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