Section 3: Safety Lighting

Description

Safety lighting may be installed at any interchange, highway intersection, or other decision-making point or points of nighttime hazard. Safety lighting may be used to the extent necessary to provide for safety enhancement and the orderly movement of traffic.
There are three kinds of safety lighting:
partial interchange/intersection
,
complete interchange/intersection
, and
spot
. Which is used depends on the warranting conditions.
Partial interchange/intersection lighting
 covers:
  • acceleration and deceleration lanes
  • ramp terminals
  • crossroads at frontage road or ramp intersections
  • other areas of nighttime hazard.
Complete interchange/intersection lighting
 covers the limits of the interchange, including:
  • main lanes
  • direct connections
  • ramp terminals
  • frontage road or crossroad intersections.
Spot lighting
 is another kind of safety lighting. Spot lighting usually consists of one to five units intended to illuminate a nighttime hazard, such as sections with complex geometry or raised channelization.
For contracting purposes, all types of safety lighting are handled in the same manner.

Eligibility

Any highway designated as part of the state highway system is eligible for safety lighting provided that TxDOT anticipates that:
  • the safety of nighttime traffic movements will be enhanced, and
  • the incidents of nighttime crashes might be minimized or eliminated.

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.
Warranting Conditions for Freeway and Expressway Safety Lighting
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.

Continuous Lighting Classified as Safety Lighting

A continuous lighting system may qualify as a safety lighting system, provided all of the following conditions are met:
  • the system is installed on a freeway with full control of access
  • the freeway passes through unincorporated areas or through incorporated areas with municipal populations of less than 50,000 people according to the latest federal census
  • the freeway has an ADT volume in excess of 70,000 vehicles, and
  • a TxDOT study of the traffic volume or nighttime crash rate of the freeway indicates that continuous lighting will substantially improve traffic safety and the efficiency of nighttime traffic.