Geometric and Operational Improvements at Continuous Flow Intersections to Enhance Pedestrian Safety

Document Type


Publication Date

Winter 12-31-2014


Traditional four-phase, four-legged intersections may operate inefficiently under high traffic demand. Innovative geometric design configurations for intersections allow more efficient traffic operations and can significantly increase vehicle throughput. Continuous flow intersections (CFIs), also referred to as displaced left-turn intersections, use an unconventional lane arrangement to maximize the vehicular throughput. This arrangement involves displacing left-turn lanes across opposing through traffic before reaching the main intersection. Such an alteration allows left-turning and through vehicles to proceed simultaneously, and both intersection capacity and delay are improved as a result. Numerous studies have validated these operational improvements, but pedestrian accommodation often is low because of the unconventional configuration. Both pedestrian crossing time and distance are longer than desired, and the unfamiliar geometry makes intersection navigation difficult and possibly unsafe for pedestrians. An enhanced CFI configuration is proposed and tested to improve the pedestrian experience. Because pedestrian crossing activity often resulted in heightened intersection delay, a flexible signal control program was developed, specifically for this intersection to reduce vehicle delay while prioritizing pedestrian crossing. The signal control procedure dynamically chooses the appropriate phase and green time combination to minimize delay by considering pedestrian wait time and existing queue length. A simulation analysis was performed with this advanced control method, and results show how its implementation can improve pedestrian accommodation while minimizing vehicle delay at CFIs.

Publication Title

Transportation Research Record




Highway Design 2014

First Page


Last Page