FHWA-SA-09-017

This case study is one in a series documenting successful 

intersection safety treatments and the crash reductions that 

were experienced. Traffic engineers and other transportation 

professionals can use the information contained in this case 

study to answer the following questions:

•	 Whataresomelow-cost countermeasures that can reducelatenight/early-morningcrashes (many with injuries)aturban andrural

intersections?

•	 How manycrashesdidthetreatments reduce?

•	 Arethereanyimplementation issuesassociated with lighting,andif so,

how can theybeovercome?

Reducing Late-Night/

Early-Morning Intersection 

Crashes By Providing Lighting

Intersection Safety Case Study

Photo by April Armstrong (used with permission).
2 FHWA | Reducing Late-Night/Early-Morning Intersection Crashes By Providing Lighting

Objective

The following case study showcases the results of three studies which examined lighting enhancements at more than 

50 intersections in Minnesota and Kentucky, installed to reduce crashes associated with poor visibility at intersections 

during late-night/early-morning hours. 

Introduction

More than 40 percent of intersection fatalities occur during the late-night/early-morning 

hours. Further, the probability of being killed in a crash during late-night/early-morning 

hours is as much as three times greater than during the day[1]. A primary reason for 

this difference in crashes is poor intersection visibility, where drivers are not able to see 

conflicting traffic and other road users. Increasing the luminance levels of existing lighting 

systems, or providing overhead lighting where necessary, can reduce late-night/earlymorning crashes at intersections. 

Treatment Summary

This case study examines the application of street lights to intersections in rural and urban areas1. While the type 

of lamp and wattage varied for some of the intersections, a single 250 watt, high pressure sodium (HPS) luminaire 

street light was installed at a majority of the intersections evaluated in these studies [3, 5]2. 

Evaluation Methodology

This case study reviews results from three studies that 

examined intersections in Minnesota and Kentucky with 

a high incidence of crashes due to poor visibility during 

late-night and early-morning hours. Crash reductions 

were based on a review of “before and after” data at these 

intersections during a minimum of six years, between 

1996–20043. (The “before” and “after” observation periods 

ranged between 36-48 months, depending on the study).

Results

Problem: Drivers were violating traffic controls at intersections 

due to poor visibility, leading to a high number of crashes at 

these intersections.

Solution: The States sought to reduce late-night/early-morning 

intersection crashes through improved lighting. The enhanced 

lighting reduced overall late-night/early-morning crashes across 

these intersections by a weighted average of 35 percent. 

1 Both of the Minnesota studies examined stop-controlled intersections. The Kentucky study did not specify the type of intersection control used.

2 The studies did not provide any additional specifications on the types of lighting used, nor whether the lighting met American Association of State Highway and 

Transportation Officials (AASHTO) standards. The Kentucky study did not specify the type of lighting used.

3 Note that crash reduction averages in this report reflect the percent reduction per year based on the difference between the total number of “before” and “after” crashes. 

Injury reductions per year are noted where supporting data were available. 

Photo by April Armstrong (used with permission).
FHWA | Reducing Late-Night/Early-Morning Intersection Crashes By Providing Lighting 3

Increasing the luminance levels 

of existing lighting systems, or 

providing overhead lighting 

where necessary, can reduce 

late-night/early-morning crashes 

at intersections.

Photo by April Armstrong (used with permission).
4 FHWA | Reducing Late-Night/Early-Morning Intersection Crashes By Providing Lighting

4 Note that crash rate is defined by the authors as crashes per million vehicles entering the intersection. 

Before After

Analysis Period

in Years Location Study Year

Reduction

in Overall Late-night/

Early-morning Crashes

Reduction 

in Late-night/Earlymorning Injury Crashes

Number of

Intersections

Minnesota 

(Study 1)

Kentucky 

(Study 2)

Minnesota 

(Study 3)

2004

2003

1999

3

4

3

3

3

3

34b

9a

12b

27%

45%

25-40%

41%

NA

8-26%

Table 1: Summary of lighting studies a

Rural and urban intersections bRural intersections

Study 1

Isebrand and McDonald (2004) analyzed the effects of street lighting on crashes at 34 rural Minnesota 

intersections before and after installing lighting[3]. The lighting installation dates ranged from 1985 to 

2000. The “before and after” analysis showed a 27 percent reduction in night crash frequency, a 32 percent 

reduction for the ratio of night to total crashes, and a 35 percent reduction in the night crash rate4. 

Late-night/early-morning injury crashes decreased by 41 percent after the lighting was installed. Latenight/early-morning crash severity (ratio of nighttime injury and fatal crashes to total crashes) 

decreased by 20 percent in the after period. 

Study 2

A “before and after” study in Kentucky conducted by Green et al. (2003) analyzed the safety benefits 

associated with roadway lighting at nine intersections[4]. The lighting installation dates varied between 

1998 and 2000. A significant number of the locations identified were rural; however, some urban sites 

were also included. The number of crashes per year was obtained for up to 4 years prior to the lighting 

installation and 3 years after installation. The analysis found that late-night/early-morning crashes 

were reduced by 45 percent after installing the lighting.

Study 3

Preston and Schoenecker (1999) conducted a “before and after” analysis for a sample of 12 intersections 

selected by Minnesota DOT[5]. At intersections where street lighting was installed (between 1987 and 

1994), researchers observed an overall decrease in the late-night/early-morning crash rate from 1.41 

crashes per million vehicles entering before lighting to 0.84 after lighting — a decrease of approximately 

40 percent in the late-night/early-morning crash rate. After installing street lighting, the late-night/earlymorning multiple-vehicle crash rates declined from 0.48 before lighting to 0.18 after lighting, a 63 percent 

reduction. The late-night/early-morning single-vehicle crash rate also declined from 1.55 before lighting 

to 1.03 after lighting, a 33 percent reduction. The results of this study concluded that installing street 

lighting at rural intersections resulted in a 25–40 percent reduction in the overall nighttime 

crashes, as well as an 8–26 percent reduction in the nighttime injury crashes.
Installing street lighting can reduce 

late-night/early-morning crashes at 

intersections by a weighted average 

of 35%.

FHWA | Reducing Late-Night/Early-Morning Intersection Crashes By Providing Lighting 5

Photo by April Armstrong (used with permission).
Discussion

Implementation Issues

The studies suggested that the states experienced no 

implementation issues with these countermeasures.

Cost

The studies did not provide any information on the costs 

to install lighting at the treated intersections. Providing 

lighting involves both fixed costs for lighting installation 

and ongoing maintenance costs. Lighting upgrades 

(installation of higher wattage bulbs) can typically cost 

up to $1,500-2,500 including labor and equipment per 

intersection. The installation of a new pole can vary 

from $3,000 to $12,000, depending on fixture type and 

conduit costs (not high mast).

Time Frame

The studies did not provide any information on the time 

needed to install lighting at the treated intersections. 

Upgrades to replace existing bulbs with higher wattage 

bulbs can take up to two hours per intersection. A 

new lighting installation generally requires a minimum 

6- to 12-month implementation period. The lighting 

system must be designed, permits approved, and onsite 

electrical power obtained. The installation itself can 

usually be completed in less than 90 days.

Effectiveness 

The enhanced lighting reduced overall late-night/

early-morning crashes across these intersections. 

Analysis conducted for the application of the lighting 

to the 12 (Study 3) intersections selected by Minnesota 

DOT determined a benefit-cost ratio of 11:1. Previously 

published research reports further confirm that installing 

intersection lighting is effective in reducing late-night/

early-morning crashes[8]. 

Summary of Results

The studies referenced here demonstrate that 

installing street lighting can reduce late-night/earlymorning crashes by a weighted average of 

35 percent. The average reductions in crashes achieved 

by the treatments is consistent with the overall crash 

reductions for lighting installations of 17-47 percent and 

50 percent reduction of nighttime crashes as mentioned 

in the Desktop Reference for Crash Reduction Factors 

(September 2007), published by the United States 

Department of Transportation (USDOT) FHWA[6].

6 FHWA | Improving Safety by Providing All-Red Clearance Intervals and Larger Signal Lenses

Photo by April Armstrong (used with permission).
FHWA | Reducing Late-Night/Early-Morning Intersection Crashes By Providing Lighting 7

References

1) Traffic Safety Facts Annual FARS, National Highway Traffic 

Safety Administration, 2008.

2) Opiela, Kenneth S., Andersen, Carl K., and Schertz, Greg. 

“Driving After Dark,” Public Roads Magazine, Vol. 66. No 4, 

January/February 2003. 

3) Isebrand and McDonald. “Safety Impacts of Street 

Lighting at Isolated Rural Intersections, Part II, Year 1 

Report,” MN/RC-2006-35, Minnesota Department of 

Transportation, December 2004. (Study 1).

4) Green, E.R., Agent, K.R., Barrett, M.L., and Pigman, J.G., 

“Roadway Lighting and Driver Safety,” KTC-03-12/

SPR247-02-IF, Kentucky Transportation Center, University 

of Kentucky and Federal Highway Administration, May 

2003. (Study 2).

5) Preston, H. and Schoenecker, T., “Safety Impacts of Street 

Lighting at Isolated Rural Intersections,” MN/RC-1999-17, 

Minnesota Department of Transportation, April 1999. 

(Study 3).

6) Federal Highway Administration. Desktop Reference for 

Crash Reduction Factors, FHWA-SA-07-015 (Washington, 

DC: September 2007), p. 43.

7) Elvik, R. “Meta-Analysis of Evaluations of Public Lighting 

as Accident Countermeasure,” Transportation Research 

Record, Transportation Research Board, The National 

Academies, 1485, pp. 112-124, 1995.

8) Neuman, T.R., et al. “Strategy 17.1 E2—Improve Visibility 

of the Intersection by Providing Lighting (P),” NCHRP 

Report 500,Volume 5: A Guide for Addressing Unsignalized 

Intersection Collisions, Transportation Research Board, The 

National Academies, pp V-70–V-71, Washington, DC, 2003.
FHWA-SA-09-017 December 2009

For More Information

Ed Rice

Intersection Safety Team Leader, 

FHWA Office of Safety

202.366.9064

ed.rice@dot.gov

Eric Green

Research Engineer, 

Kentucky Transportation Center

859.257.2680

egreen@engr.uky.edu

Susan Zarling

Office of Traffic Safety,

Minnesota Department of Transportation

651.234.7052

susan.zarling@state.mn.us