Background / Overview

Light Emitting Diode (LED) traffic signals are energy efficient and have a longer life when compared to incandescent lamps. This directly translated to savings in energy and maintenance costs. However their initial costs are significantly greater than incandescent bulbs. The Energy Policy Act of 2005 placed energy consumption criteria on traffic signal modules manufactured after January 1, 2006 and effectively eliminates the use of incandescent bulbs in traffic signal modules. Some of the issues to be concerned about LED traffic signal modules are:

  • Degradation of light output with time
  • Benefit-cost analyses
  • Monitoring, maintenance and replacement

Degradation of light output

Unlike incandescent signals, LED signals do not suffer from catastrophic failures; rather the light output gradually diminishes with time. Therefore, agencies face a different issue: when to replace the LED modules. ITE Specifications require the LED signal modules to have a minimum value for light output.

Benefit-cost analyses

Listed below are some of the Benefit-cost analyses for LED conversions

  • Springfield, MO
  • 136 intersections converted to LED signals
  • Actual energy savings (for 6 intersections) ranged from 66% to 86%
  • Estimated total energy savings 1.5 Giga Watt hours
  • Annual relamping/maintenance costs reduced from $37,700 to $3,700.
  • Payback period of 5 years
  • Little Rock, AR
  • 263 intersections converted to LED signals
  • Actual energy savings (for 10 intersections) was 57%
  • Estimated annual energy cost savings of $111,000
  • Denver, CO
  • 1200 intersections converted to LED signals
  • Net acquisition cost $1.3 M
  • Payback period of 4.28 years

Replacement Strategies

NCHRP funded Lighting Research Center (Rensselaer Polytechnic Institute) to develop recommendations for LED traffic signal replacement

  • Group replacement better than spot replacement and saves costs
  • For a 10-year operating life, replacement period of 8 years minimizes overall replacement costs. Twelve percent are replaced each year
  • For a 7-year operating life, replacement period of 6 years minimizes overall replacement costs. Seventeen percent are replaced each year

National Practices

National survey of public agencies was conducted by an ITE Task Force. 76 agencies responded. Key findings include:

  • 73% use 5-year warranty (10% do not specify warranty)
  • 60% have no monitoring/replacement procedure
  • 78% have inadequate/no funding for monitoring/replacement programs
  • Replacement approach:

Indiana

  • Six-year replacement schedule (not for yellow LED modules)
  • Aerial inspection and cleaning on a 3-year cycle

Illinois

  • No replacement policy
  • Annual visual inspection along with other traffic signal components

Road Commission of Oakland County, Michigan

  • Based on in-service evaluation expected life of 8-10 years
  • Replace 10% each year

Current Wisconsin Practices

Wisconsin has been using LED signal modules on all state intersections since 2004. All new installations are required to be LED. No LED replacement policy.

Additional Resources

  • Replacement Processes for Light Emitting Diode (LED) TrafficSignals. NCHRP Web-only Document 146, Aug 2009.
  • Led Traffic Signal Lamps:An Evaluation of Springfield Missouri’s Experience, July 2009.
  • NCHRP Synthesis 387. LED Traffic Signal Monitoring, Maintenance and Replacement issues.Tom Urbanik. 2008.
  • A Survey of Maintenance Practices of Light-Emitting Diode Traffic Signals andSome Recommended Guidelines. Behura, N. ITE Journal, April 2007.
  • Vehicle Traffic Control Signal Heads—Light Emitting Diode Circular Signal Supplement, ITE, June 2005.
  • Vehicle Traffic Control Signal Heads—Part 3: Light Emitting Diode Vehicle Arrow Traffic Signal Modules, ITE, Jan 2008.

Wisconsin Traffic Operations and Safety (TOPS) Laboratory

Institute of Transportation Engineers-Wisconsin Section