Exploring the Safety Benefits of All-Way Stop Control at Low-Volume Unsignalized Intersections

One of DelDOT’s emphasis areas in the 2021-2025 Delaware Strategic Highway Safety Plan (SHSP): Towards Zero Deaths, is Intersections. From 2015 through 2019, nearly 40 percent of fatalities and serious injuries in Delaware occurred at an intersection. Of the fatalities and serious injuries that occurred at an intersection, 51 percent occurred at unsignalized intersections.

In support of the SHSP objective to reduce intersection fatalities and serious injuries by 15 percent over the next five years, DelDOT studied the potential safety benefits of installing All-Way Stop Control (AWSC) at low-volume intersections to determine if the use of AWSC conversion could improve safety. DelDOT frequently evaluates the potential to convert intersections to AWSC based on guidance contained in the Manual on Uniform Traffic Control Devices (MUTCD). In 2017, FHWA issued Interim Approval for Optional Use of an Alternative Signal Warrant 7 – Crash Experience (IA-19). While developed for signal warrant analyses, DelDOT used these reduced thresholds to identify low-volume intersections in Delaware that could potentially benefit from AWSC.

DelDOT implemented AWSC at 20 low-volume intersections. The group of 20 intersections included roadways with varying speed limits, functional classifications, and average daily traffic. DelDOT then performed a before/after study to evaluate and identify the benefits of AWSC as a potentially cost-effective safety treatment. The data showed significant reductions in crashes, including a 75 percent reduction in fatal crashes and a 90 percent reduction in injury crashes.

The implementation and evaluation of AWSC at unsignalized intersections is consistent with DelDOT’s SHSP strategy to reduce the frequency and severity of intersection crashes through operational, geometric, and traffic control device improvements. Traffic control devices needed to implement AWSC (signs and, in some cases, pavement markings and solar powered beacons) are low cost, minimally invasive, and can be installed quickly. DelDOT’s research efforts have shown that implementing AWSC as a countermeasure at low-volume intersections has a high potential for significantly reducing fatal and serious-injury crashes while using planning and engineering resources efficiently.

Additional Information

Senator Tom Carper (D-DE), Chair of the Senate Environment & Public Works Committee, greets Delaware constituents, including Peter Haag, Chief of Traffic Engineering at DelDOT.