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
Unsignalized intersections where crash data shows a high occurrence of crashes where vehicles on secondary roadways intersecting at grade misjudge the gap between approaching vehicles.
This diagram represents one example of how such a system of pavement markings and signs may be used.
The lack of adequate sight distance at unsignalized intersections may reduce the ability of drivers to see an approaching vehicle and/or judge the suitable available gap for making turning and crossing maneuvers. Even where sight distance is adequate, drivers may ignore traffic control devices such as stop or yield signs and may misjudge available gaps in traffic. Thus, intersection crashes may occur because drivers are unable to judge adequately the distance and time to an approaching vehicle. This strategy involves the use of innovative signing and passive markings to assist drivers in deciding when to accept a gap. The markings could take the form of pavement markings placed in the field of view of a driver observing the approaching traffic stream. Drivers would need to be told, by signing or through a public education campaign, not to proceed when an approaching vehicle is closer to the intersection than the pavement marker. In the illustration above, the entire treatment consists of the following components:
It is very important that a driver on the secondary road, while stopped to make the decision whether to enter the intersection, can clearly view the "Look Left-Right-Left Before Pulling Out" warning sign. If the warning sign is not easily viewed from the decision point on the secondary road, it should be shifted to a more visible location.
This strategy is considered experimental. If an agency desires to pursue its application, it is recommended that the agency proceed with caution, conducting pilot tests in conjunction with a carefully planned evaluation.
Time frame for implementation can generally be short if right-of-way is available.
Costs are generally low for a simple system but will increase for more complex systems.
EXPERIMENTAL: This strategy has been experimented with in few locations with no conclusive results. Pennsylvania has experimented with a similar type of countermeasure.
This strategy can be used in conjunction with most other strategies for improving safety at unsignalized intersections.
The information in this fact sheet differs from that presented in the NCHRP Report 500, Volume 5. The countermeasure discussed in the report was found to not increase safety and therefore is not recommended.
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