Measuring Modern Roundabout Traffic Conflict Exposure

Abstract

This article provides a safety analysis on Wisconsin roundabouts using crash records and field video data. Crash records at 41 roundabouts were retrieved from an online database, and field video data were collected at two multilane roundabouts. The percentages of each of the seven identified crash types is estimated by averaging the crash type percentage of all 41 roundabouts. It is found that the most common crash type at single-lane roundabouts is entering-circulating crashes, whereas sideswipe crashes have a higher percentage at multilane roundabouts than at single-lane roundabouts. To examine the relationship between driver behavior and crash patterns at multilane roundabouts, field video data from two multilane roundabouts were used to quantify 12 types of undesired negotiation activities. The ratio of the number of undesired negotiations to the traffic count is defined as the exposure rate (to conflicts). The exposure rate can be utilized to estimate the crash type percentage. Although the chi-squared statistical test did not support the hypothesis of same crash type distribution between the expected crashes and actual ones, the exposure rates successfully identified the entering-circulating and sideswipe (in circulating lanes) crashes as the two major crash types.