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FHWA Home / Safety / Intersection / Low-Cost Safety Enhancements for Stop-Controlled and Signalized Intersections

Low-Cost Safety Enhancements for Stop-Controlled and Signalized Intersections

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4. Lighting at Unlit or Poorly Lit Intersections

Crash Problem

Crashes that occur during darkness are typically more severe than daylight crashes. Major problems associated with unlit or poorly lit intersections (e.g. only one light per intersection) include reduced ability to recognize that an intersection is being approached, reduced ability to navigate turning movements properly, and degradation of the ability to recognize other vehicles and pedestrians in or entering the intersection.

Countermeasures

The low-cost countermeasure for unlit or poorly lit intersections with a high frequency and rate of night crashes is lighting. Typical example layouts for intersection lighting are shown in Figures 4 and 5. States should follow their design policy for intersection lighting installations.

Figure shows the intersection of two two-way roads where light posts are mounted above the stop bar on each stop approach.
Figure 4: New Design for Intersection Lighting Layout
Source: Federal Highway Administration, Informational Report on Lighting Design for Midblock Crosswalks, FHWA-HRT-08-053 (Washington, DC: April 2008).

Figure shows the intersection of a two-way road with a four-lane road where light posts are mounted above the stop bar on each stop approach. Because the four-lane road has two lanes on the stop approach, additional lighting is mounted on a median strip that divides the opposing traffic, so the left lane and right lane stop approach are both illuminated at the stop bar.
Figure 5: New Design for Wide Roadway Intersection Lighting Layout
Source: Federal Highway Administration, Informational Report on Lighting Design for Midblock Crosswalks, FHWA-HRT-08-053 (Washington, DC: April 2008).

Countermeasure Crash Reduction Factors, Threshold Levels, Additional Implementation Factors, and Estimated Cost Ranges

The crash reduction factor at unlit intersections with high frequencies and rates of night crashes is 50 percent of night crashes. The crash reduction factor for improving lighting at poorly lit intersections is estimated by an expert safety panel as 25 percent of night crashes.

Typical threshold crash levels for considering lighting countermeasures at intersections are provided in Table 4.

Table 4: Crash Reduction Factors, Typical Crash Thresholds, Additional Application Factors, and Estimated Implementation Cost Ranges for Lighting Countermeasures at Unlit or Poorly Lit Intersections
Countermeasure Crash Reduction Factor Typical Urban Crash Threshold Typical Rural Crash Threshold Additional Intersection Concern Implementation Cost Range per Intersection
New or upgraded lighting 50% (NEW), 25% (UPGRADED) of night crashes 10 night crashes in 5 years and a night /total crash ratio above the statewide average for urban unlit intersections 5 night crashes in 5 years and a night/total crash ratio above the statewide average for rural unlit intersections None $5,000 to $15,000
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Page last modified on September 4, 2014.
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