Complex Traffic Light Timing

In many accidents, determining who had the right-of-way involves the color of the traffic light for each driver. A traffic engineer has defined the type and sequence of traffic lights at an intersection and how the timing is affected by the amount of traffic.

We use the traffic signal timing diagrams and layout drawings to understand how the signals operate. Then we evaluate the statements of witnesses and participants in an accident to determine possible traffic signal states for each driver under various scenarios. We use the possible traffic signal states, witness statements and the reconstruction of the motions and timing of the vehicles to determine the most probable sequence of events leading up to the accident.

When traffic lights are involved in an accident, we usually look at:

• Who had the green light or turn arrow
• The sequence of the traffic lights
• The minimum/maximum time at each state (green, yellow and red)
• The locations of triggers for the traffic lights (inductive loops)
• How other vehicles affected the traffic lights