Generally, how is traffic volume related to crashes?

The relationship between traffic volume and crashes is well established in road safety studies. When traffic volume increases, the frequency of crashes tends to increase as well. This is primarily due to the higher number of vehicles on the road, which can lead to more interactions (and potential conflicts) between road users. More vehicles can also mean more congestion, which can exacerbate the chances of accidents as drivers may become impatient or engaged in risky behavior.

However, the severity of crashes can actually decrease with an increase in traffic volume for a few reasons. In densely packed traffic situations, speeds often decrease, which tends to limit the potential impact force during crashes. Lower speeds are associated with less severe accidents, as the dynamics of a collision at lower speeds result in less serious injuries compared to collisions at higher speeds. Therefore, under certain conditions, while the number of crashes may rise due to increased volume, the severity of those accidents may indeed decrease.

This nuanced understanding highlights why the increase in traffic volume correlates with higher crash frequency while often resulting in lower crash severity, especially in urban settings where vehicles are generally moving at slower speeds due to traffic congestion.