In Germany, a simulation study found that with 50 percent of vehicles equipped, the braking control features of a collision avoidance system would contribute to a 45 to 60 percent decrease in collisions when the leading vehicle brakes.

8-12 November 1999

Summary Information

The simulation study described in this report investigated the safety impacts of a collision avoidance system that used longitudinal vehicle control to attempt to prevent crashes. The system simulated included microwave radar and computer vision technologies mounted on the front portion of the vehicle. The system uses information gathered by these sensors to control vehicle speed via actuators that allowed the control of acceleration and braking. Braking is automatically controlled only at the latest possible moment to avoid collision if the driver has not applied the brakes.

The simulations carried out in this study were developed based on field measurements of performance of the system in and around the city of NordHausen, Germany. The performance measurements for the collision avoidance were taken at a closed test facility. Some model parameters were gathered from a trial of an advanced collision warning system using many of the same technologies to provide audio, visual, and physical warnings to drivers of impending collisions. This system was tested in rural and urban areas around NordHausen. Additional parameters for platoon conditions in the simulation were gathered from observation of traffic on a three-lane motorway.

The study measured the frequency of collisions during numerous simulations of platoons of vehicles operating under a variety of scenarios. In each situation, the lead vehicle in a platoon decelerates to simulate an unsafe maneuver. Simulation scenarios varied due to changes in a series of parameters, including:
  • The deceleration rate of the lead vehicle.
  • The target speed of the lead vehicle (either a full stop, or half of the initial speed).
  • The percentage of vehicles in the platoon equipped with collision avoidance systems (0, 10, 25, and 50 percent).

Reductions in the number of accidents when comparing various levels of market penetration of the collision avoidance to the base case of no vehicles with the system ranged considerably under the circumstances investigated during the study. The smallest reduction was 9 percent when the lead vehicle brakes at the maximum rate to a complete stop and 10 percent of the vehicles in the platoon have collision avoidance system. The greatest reduction was a 60 percent reduction in the number of collisions when the lead vehicle brakes at 20 percent of the maximum rate to a complete stop and 50 percent of the vehicles in the platoon have collision avoidance systems. The following table lists more detailed results.

Lead Vehicle Maneuver
Number of accidents with no equipped vehicles
Percent accident reduction with varying market penetrations
10% Penteration
25% Penetration
50% Penteration
Braking at 20% of max rate to full stop
32,730 crashes
Braking at 40% of max rate to full stop
Braking at max rate to full stop
22 %
Braking at max rate to half initial speed
11 %
25 %

Additional analysis of the simulation results under the various scenarios yielded the following observations:
  • Equipped vehicles in the center lane of the 3-lane motorway obtain a slightly higher benefit from the system (approximately 2 percent).
  • The slow lane has the lowest number of accidents.
  • The collision avoidance system is most effective in preventing primary accidents, less effective in preventing secondary collisions.
  • The number of swerving maneuvers are reduced with increasing percentage of equipped vehicles; the consequences of swerving also diminish as the percentage of equipped vehicles increases.


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The Evaluation of Impact on Traffic Safety of Anti-Collision Assist Applications

Author: Sala, Gianguido and Lorenzo Mussone

Published By: Paper presented at the 6th World Congress on ITS. Toronto, Canada

Source Date: 8-12 November 1999


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Benefit ID: 2000-00159