Evaluating Permitted/Protected Versus Protected Left Turn Signals in Louisiana

The primary objective of this project is to study the safety and operation of existing signalized intersections (protected only versus permitted/protected left turns versus permitted only but with left turn lanes) along with their geometric features, as described in the Department of Transportation and Development (DOTD) Traffic Signal Manual, with the view to develop guidance on when it is appropriate to install each signal type. The research will answer whether or not the signal type affects the intersection control delay as well as if the signal type affects crash type and frequency. It will also investigate which geometric features significantly impact on the choice of signal type and if flow characteristics (traffic volumes) influence crash characteristics, and ultimately the choice of signal type. Finally, the research will explore when it is most appropriate to install a specific signal type considering operation and safety concerns.