J. Zhao, H. Zhou, H. Chen, P. Hsu

Pages: 75-90

Abstract
The traffic flow at three left exits was recorded and data including vehicle speed, traffic volume, lane change maneuver, traffic conflict and exit geometric configuration were collected. The crash records for 11 left exits and 63 right exits were collected as well. The data analysis results showed that speed deviations on optional lanes at the left exits were less than 25 kph and will not cause a big safety issue. The observational study indicated that about 3% to 6% vehicles made lane change maneuvers along the 1000 feet freeway segment before the left exits, and the traffic conflict rate on the same freeway segment was approximately 10-13 per 1,000 vehicles. The cross sectional comparison study indicated that the crash rate and annual average crash frequency for left exits were higher than that for right exits. For one-lane exits, the percent of injury plus fatal crashes in total crashes for left exits were also significantly higher than that for right exits. However, the differences between left and right exits were not significant for two-lane exits. Future research on traffic sign for left exit and traffic conflict study on right exit were also recommended at the end of the paper.

Keywords: left exit; lane change maneuver; traffic conflict study; cross sectional comparison study