HEAD-ON, LEFT-TURN ACCIDENTS AT INTERSECTIONS WITH NEWLY INSTALLED TRAFFIC SIGNALS

Installations of traffic signals at intersections are often associated with changes in the accident characteristics at those sites. Past studies have indicated a reduction in the severity of accidents, but in some instances accident frequencies have increased. Traffic signlas also influence changes in the distribution of accident types. Head-on, left-turn accidents at signalized intersections are of great importance to traffic engineers. A study of newly installed traffic signals was performed in Michigan to evaluate the changes in the distribution of accident types, including head-on, left-turn accidents. This study involved statistical testing of before and after accident rates at groups of similar intersections. The results of this study indicated an increase in head-on, left-turn accidents at the group of signalized intersections with and without separate left-turn lanes. However, the rate of increase in such accidents at locations without a separate left-turn lane was not significant at the 95% confidence level. The group of locations in which a separate left-turn lane was installed along with the traffic signals also did not indicate a statistically significant change in the head-on, left-turn accident rate.