Study of Signal Timing and Traffic Design Methods for Roundabouts

The left-turn with two stops (LWTS) method is commonly used for roundabouts as an effective way to avoid traffic conflict. This study is aimed at the signal timing and traffic design for roundabouts with LWTS. We recommend lamps with only motor vehicle signal and discuss the locations of the signal lamps. We also propose circle signs and linear inducing signs for roundabouts. The behavior and needs of pedestrian and bicycle crossings were also considered in LWTS. Lastly, an improved signal timing method was recommended for roundabouts. The city of Shangqiu was used as an example. Results show that the LWTS method has a high release efficiency and the given timing method is suitable for the roundabouts. No overflow occurred during the period of operation. The signal timing and traffic design method proposed here for LWTS control will be a guideline for roundabouts with similar features.