Warrants
Conditions warranting safety lighting vary depending on the type of roadway (freeway, expressway, or other designated on-system highway) and whether the proposed lighting is partial interchange, complete interchange, or spot.
Freeways and Expressways.
For freeways and expressways, safety lighting may be warranted under one of the conditions described in the following table.Type of Lighting | Case | Warranting Conditions |
|---|---|---|
Partial Interchange/ Intersection | SL-1 | Current average daily traffic (ADT) ramp traffic entering and leaving the freeway within the interchange area exceeds 5,000 for urban conditions or 3,000 for suburban conditions or 1,000 for rural conditions. |
SL-2 | Current ADT on the through traffic lanes exceeds 25,000 for urban conditions, 20,000 for suburban conditions, or 10,000 for rural conditions. | |
SL-3 | Ratio of night to day crash rates within the interchange area is at least 1.25 times the statewide average for all similar unlighted sections, and a study indicates that lighting may be expected to result in a significant reduction in the night crash rate. NOTE: Because the ratio of night to day crash rates for a given section of roadway cannot always be statistically verified, this measure must be considered as an aid to design rather than an absolute rule. Engineering judgment should be exercised when using this warrant. | |
Complete Interchange/ Intersection | SL-4 | Current ADT ramp traffic entering and leaving the freeway or expressway within the interchange areas exceeds 10,000 for urban conditions, 8,000 for suburban conditions, or 5,000 for rural conditions. |
SL-5 | Current ADT on the crossroad exceeds 10,000 for urban conditions, 8,000 for suburban conditions, or 5,000 for rural conditions. | |
SL-6 | Existing substantial commercial or industrial development that is lighted during hours of darkness, is located in the immediate vicinity of the interchange , or where the crossroad approach legs are lighted for 0.5 miles or more on each side of the interchange . | |
SL-7 | The ratio of night to day crash rates within the interchange area is at least 1.5 times the statewide average for all unlighted similar sections, and a study indicates that lighting may be expected to result in a significant reduction in the night crash rate. NOTE: Because the ratio of night to day crash rates for a given section of roadway cannot always be statistically verified, this measure must be considered as an aid to design rather than an absolute rule. Engineering judgment should be exercised when using this warrant. |
Other Designated On-System Highways.
For streets and highways other than freeways, AASHTO has not established safety lighting warrants for the installation of roadway lighting that satisfy all conditions. In general, lighting may be considered for those locations where the relevant governmental agencies agree that lighting would contribute substantially to the safety, efficiency, and comfort of vehicular and pedestrian traffic.
Spot Safety Lighting.
Spot safety lighting may be used at intersections or other areas where lighting will provide safer movement of traffic.