According to recent research from the Texas Transportation Institute, traffic congestion in the majority of major urban areas in the United States is increasing. What is the impact of traffic congestion on traffic accident rates? A recent study in Detroit, Michigan examined a 16-mile segment of the Interstate over a 2 year period. They investigated relationships between different levels of traffic congestion, measured by volume to capacity (v/c) ratios, and traffic accident rates, measured by crashes per 100 million vehicle miles travelled (VMT). They found that, overall, traffic accident rates are very high at low levels of traffic congestion but quickly decrease with increasing v/c ratios, before gradually increasing again at peak levels of traffic congestion. However, fatal and injury traffic accidents tend to decrease steadily as v/c ratios increase.
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