Performance Effects of the New Displaced Left Turn and Median U-Turn Combination Design

Abstract

During the last two decades, transportation professionals have turned to alternative intersection designs with two critical signal phases, such as median U-turn (MUT) and reduced conflict intersections (RCIs), to improve safety and mobility. Intersections with two critical signal phases often have substantial safety and performance benefits. Nonetheless, two-critical-phase designs may lack public acceptance and may have noticeable impacts at some intersection sites owing to the substantial changes required to convert a four-phase traffic signal to a two-phase traffic signal. Conversely, three-critical-phase designs might mitigate some of these issues because only one of the signal phases will be removed (compared with a four-phase signal), but they may still present some of the benefits of two-phase designs. This study utilized microsimulation to analyze the performance effects of a new three-phase design, the partial displaced left turn and median U-turn combination (DLT/MUT combination), a partial DLT, and an existing (conventional) intersection at two intersection sites in North Carolina. The results showed that the partial DLT/MUT combination can outperform the conventional intersections in high-traffic volume scenarios. On average, this new design reduced vehicle travel time by 63% and 21% in comparison to the conventional intersection in case study sites #1 and #2, respectively. It also performed similarly with the partial DLT in operations, but it should be safer and more friendly to people walking and biking, and more cost-effective.