Journal of the South African Institution of Civil Engineering
On-line version ISSN 2309-8775
NAGHAWI, H H and IDEWU, W I A. Analysing delay and queue length using microscopic simulation for the unconventional intersection design Superstreet. J. S. Afr. Inst. Civ. Eng. [online]. 2014, vol.56, n.1, pp. 100-107. ISSN 2309-8775.
With the increasing demand on today's roadway systems, intersections are beginning to fail at alarming rates prior to the end of their design periods. Therefore, maintaining safety and operational efficiency at intersections on arterial roadways remains a constant goal. This effort for sustainability has spawned the creation and evaluation of numerous types of unconventional intersection designs. Several unconventional designs exist and have been studied, including the Bowtie, Continuous Flow Intersection, Paired Intersection, Jughandle, Median U-Turn, Single Quadrant Roadway and Superstreet Median. Typically, these designs eliminate/reroute conflicting left-turn manoeuvres to and from the minor or collector cross road. High left-turning volumes are addressed by adding an exclusive left-turning signal. This consequently increases the required number of signal phases and shorter green time for the major through traffic. This paper describes the evaluation of an unconventional intersection designed to lessen the effects of high left-turning traffic. To aid in the evaluation of the unconventional Superstreet design, a comparison of a Conventional intersection's operation was made. Constructing and analysing a live Superstreet and Conventional intersection design is a massive undertaking. Microscopic traffic models were developed and tested using CORSIM. A variety of scenarios were created by changing the approach volumes and turning percentages on the major/minor roads to reflect different congestion levels that may occur at the intersection on any given day. The total number of created scenarios was 72, i.e. 36 scenarios for each design. Among the general findings of this research was that the Conventional design consistently showed evidence of higher delay time and longer queue length compared to the Superstreet intersection design. The reduction in the network delay ranged from 27.39% to 82.26%, and an approximate 97.5% reduction in average network queue length experienced on the major road's through lanes when the Superstreet design was implemented. This is a significant reduction, especially since the through lane volume of the major road is relatively high. These results are assumed to be due to the additional available green time for the Superstreet intersection design.
Keywords : superstreet; unconventional intersection design; microscopic simulation; CORSIM.