The Effect of Using the Same Tire Friction for Both Vehicles in Impact Speed Reconstructions
Most collision reconstructions implicitly assume the same tire/road friction coefficient for all vehicles, despite evidence that friction varies between tires, surfaces, and individual trials. Here we assess the errors introduced by an assumption of a single, universal friction coefficient when reconstructing a collision where vehicles actually had different tire frictions. We used Monte Carlo methods to generate 20,000 synthetic two-vehicle impacts and rest positions using different, randomized friction coefficients for each vehicle and randomized impact speeds. These rest positions were then used to reconstruct both vehicles’ impact speeds assuming a single, common friction coefficient. High and low bounds on the impact speeds were reconstructed using high and low bounds on the common friction. We found that more than 97% of the true impact speeds were in the ranges reconstructed using upper and lower friction bounds.