U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
NCHRP Report 500 / Volume 5: A Guide for Addressing Unsignalized Intersection Collisions
Photo by: FHWA
All-way stop control can reduce right-angle and turning collisions at unsignalized intersections by providing more orderly movement at an intersection, reducing through and turning speeds, and minimizing the safety effect of any sight distance restrictions that may be present. However, all-way stop control is suitable only at intersections with moderate and relatively balanced volume levels on the intersection approaches. Under other conditions, the use of all-way stop control may create unnecessary delays and aggressive driver behavior (e.g., deliberate ignoring of the stop control).
Identify moderate volume situations where all-way stop control will operate efficiently without substantially more delay than a signalized intersection.
It is important that the driving public be alerted to the change of control during a transition period.
Not every two-way stop-controlled intersection should be considered as a candidate for all-stop control. This strategy should be used selectively, recognizing traffic volumes and patterns and potentially adverse reaction by the driving population to being stopped for no apparent reason. If drivers encounter substantial delays, they may become impatient and act irrationally, which can lead to crash patterns of the type that the strategy is intended to correct.
All-way stop control can normally be implemented with just a change in signing at the intersection or on intersection approaches, typically in 3 months or less.
The costs involved in converting to all-way stop control are relatively low. However, an agency's maintenance costs may increase.
PROVEN: A recent review of the effectiveness of various strategies in reducing crashes concluded that conversion from two-way to all-way stop control could reduce total intersection crashes by 53%. Another study determined that converting to an all-way stop from a two-way stop may reduce overall crashes at urban locations by up to 71%. Similarly, reductions were seen for left-turn crashes (20%), right-angle crashes (72%), rear-end crashes (13%), and pedestrian crashes (39%).
This strategy can be used in conjunction with most other strategies for improving safety at unsignalized intersections.
Drivers understand all-way stop control with no need for special public education campaigns. However, public information should be distributed about any forthcoming change in traffic control.
For more details on this and other countermeasures: http://safety.transportation.org
For more information contact:
FHWA Office of Safety Design
E71, 1200 New Jersey Avenue SE
Washington, D.C. 20590
FHWA Resource Center – Safety and Design Team
19900 Governor's Drive, Suite 301
Olympia Fields, IL 60461