Traffic behavior studies were conducted at seven lane-drop locations, representing three lane-drop classes. These studies consisted of conflict observations (that is, erratic movements and brakelight applications), spot-speed observations, and lane volume counts. Such a study was made before and after each different traffic control device installation in an attempt to determine which device was the most effective in minimizing conflicts at existing lane drops. A study of conflict deviations indicates that no single type of traffic control device studied was significantly effective in reducing erratic movement and brakelight rates at all seven lane-drop locations. Rather, it appears that different traffic control devices are generally most effective at each of the locations. The single-lane exit without taper constituted the lane-drop classification with the lowest conflict rates. Those lane drops with poorer sight geometries were observed to have higher conflict rates. No definitive relationship between traffic conflict rates and either volumes or accident rates was found for the lane drops studied. Certain data limitations were discovered.

Report Date


Report Number

No. 389

Digital Object Identifier



Prepared for Presentation to the 44th Annual Meeting of the Institute of Traffic Engineers (September 15-20, 1974: Detroit, Michigan).