Intersection Safety Case Study Summary

Reduce Late-Night/Early-Morning Intersection Crashes by Providing Lighting

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FHWA Office of Safety logo: Safe Roads for a Safer Future – Investment in roadway safety saves lives.

Federal Highway Administration
Office of Safety

FHWA-SA-09-017


slide notes:

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:

  • What is an inexpensive treatment option to reduce crashes, particularly right-angle crashes (many with injuries), during late-night/early-morning hours?
  • How many crashes did this treatment reduce?
  • Are there any implementation issues associated with this treatment, and if so, how can they be overcome?


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The Challenge

  • More than 40 percent of intersection fatalities occur during late-night/early-morning hours1.
  • Driver failure to see conflicting traffic and/or road users during late-night/early-morning hours is a common problem.
  • Providing lighting increases intersection visibility and reduces the number and severity of crashes during late-night/early-morning hours.

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1Traffic Safety Facts Annual FARS, National Highway Traffic Safety Administration, 2008.

slide notes:

More than 40 percent of intersection fatalities occur during the late-night/early-morning hours (SOURCE: Traffic Safety Facts Annual FARS, National Highway Traffic Safety Administration, 2008.)

A major problem is driver failure to see conflicting traffic and/or road users. Past research has shown that enhancements such as providing overhead lighting can improve intersection visibility and reduce the number and severity of crashes during the late-night/early-morning hours.



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Solution

  • "Before and After" Lighting Studies:
    • Study 1 analyzed 34 rural intersections in Minnesota. Lighting installation dates varied between 1985 and 2000. Study period was for 3 years before and after lighting was installed.
    • Study 2 analyzed 9 urban and rural intersections in Kentucky. Lighting installation dates varied between 1998 and 2000. Study period was for 4 years before and 3 years after lighting was installed.
    • Study 3 analyzed 12 rural intersections in Minnesota. Lighting installation dates varied between 1987 and 1994. Study period was for 3 years before and after lighting was installed.

Photo of a street light illuminating a red stoplight in the evening.


slide notes:

This case study examines the results of three studies which evaluated lighting enhancements at 55 intersections in Minnesota and Kentucky that reduced crashes in rural and urban areas.



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Technical Data

  • Location:
    • 55 locations in Minnesota and Kentucky
  • Implementation Cost:
    • $1,500 - $2,500 for lighting upgrades
    • $3,000 - $12,000 for new lighting installations (not high mast)
  • Implementation Time:
    • Typically 3 months
  • Implementation Issues:
    • No implementation issues were experienced

slide notes:

None.



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Results at Treated Intersections

  • Weighted Average Crash Reduction:
    • 35% reduction in late-night/early-morning crashes

Two photos, one of a stop sign illuminated by a street light, the other of a stop light illuminated by a street light.


slide notes:

These results are based on a review of data from 'before and after' study, conducted over a minimum duration of 6 years at each intersection, between 1996 – 2004. (The "before" and "after" observation periods each ranged between 36-48 months, depending on the study).

The safety enhancement discussed in this case study were added to reduce crashes. The enhanced countermeasure reduced overall late-night/early-morning crashes across these intersections by a weighted average of 35 percent. The three studies that this case study examines include:

1) Isebrand and McDonald, Minnesota, 2004 (AVERAGE LATE-NIGHT/EARLY-MORNING CRASH REDUCTION: 27%, with 41% reduction in injury crashes)

2) Green et al., Kentucky, 2003 (AVERAGE LATE-NIGHT/EARLY-MORNING CRASH REDUCTION: 45%)

3) Preston and Schoenecker, Minnesota, 1999 (AVERAGE LATE-NIGHT/EARLY-MORNING CRASH REDUCTION: 25-40%, with 8-26% reduction in injury crashes)

The average reductions in crashes achieved by this treatment 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 Department of Transportation (USDOT) Federal Highway Administration (FHWA).

Note that crash reduction averages in this report reflect the percent reduction based on the difference between the total number of "before" and "after" crashes, calculated on a per year basis.

NOTES:
This is of course a summary. Please see the Case Study for details.



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For More Information

Visit FHWA's intersection safety web site to download this and other case studies highlighting proven intersection safety treatments from across the country: http://safety.fhwa.dot.gov/intersection/

Or Contact:

Ed Rice
Intersection Safety Team Leader,
FHWA Office of Safety

Phone: 202.366.9064
Email: ed.rice@dot.gov

Susan Zarling
Office of Traffic Safety, Mn/DOT,
Roseville, MN

Phone: (651) 234-7052
Email: susan.zarling@state.mn.us

slide notes:

Again, this is one of a series of case studies documenting proven intersection safety techniques implemented across the country. Check out all of the summaries on the Office of Safety's intersection safety web site at the address above. You can also contact Ed Rice from the FHWA Office of Safety, or Susan Zarling, Minnesota Department of Transportation, for more information.


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U.S. Department of Transportation
Federal Highway Administration