The purpose of the proposed project is to find ways to mitigate the concerrns raised by pedestrians and bicyclists to superstreets. The project will have two specific objectives. First, the researchers will recommend changes in superstreet design and operation practices to overcome the objections. It is likely that some small, subtle, and inexpensive tweaks to current practices could help overcome most objections. Second, the researchers will develop materials that NCDOT can use to reach out to pedestrians and bicyclists during the planning and design stages for a superstreet project to educate them on how they may benefit from and safely and efficiently use this type of intersection.
The objective of this research was to consider the unique challenges for pedestrians and bicyclists at superstreet intersections and recommend crossing alternatives for both users. For pedestrians the options included the diagonal cross, median cross, two-stage Barnes Dance cross and midblock cross. For bicyclists the options included the bicycle U-turn, bicycles using the vehicle U-turn, the bicycle direct cross and the midblock cross. These options were analyzed through microsimulation based on average stopped delay per route, average number of stops per route, and average travel time per route. Furthermore, various parameters were analyzed per each of the crossing geometries including two signal cycle lengths, two signal splits, two signal offset designs, and two midblock distances. The results for pedestrians showed that the two-stage Barnes Dance crossing produced the lowest values for average stopped delay, average number of stops, and average travel time. However, since the Barnes Dance is designed for an intersection with high volumes of pedestrians, the pedestrian option recommended for most superstreets was instead a combination of the diagonal cross with the midblock cross. The levels that ultimately influenced travel time for pedestrians were a cycle length of 90 seconds rather than 180 seconds, a signal split of 60/40 rather than 75/25, and an offset signal design where the vehicle platoons arrived at different times rather than simultaneously. The results for bicyclists showed that the bicycle direct cross had the lowest average number of stops and the lowest average travel time. The bicycle option with the lowest stopped delay was the vehicle U-turn. The levels that produced lower travel time values for bicyclists included a cycle length of 90 seconds, a signal split of 75/25, and situations where the vehicle platoons arrived at different times rather than simultaneously.
The recommended bicycle options for the superstreet were the bicycle direct cross and the midblock cross implemented together. Additionally, the research outcomes include suggestions for public outreach materials in the form of a brochure and discussions with public groups.
