Skip Maine state header navigation

Agencies | Online Services | Help

Skip First Level Navigation | Skip All Navigation

Home > Technical Subjects >Traffic Issues>Using LED’s in Traffic Signals

Using LED’s in Traffic Signals

It has come to the DOT’s attention that many municipalities are changing from conventional signal heads(with incandescent bulbs) to LED signal heads. The Department recognizes the many advantages of the LED signal heads and is more than satisfied with their performance. However, municipalities need to be aware of potential pitfalls in using this new technology. At many intersections, it is difficult to really see which light is really on. 

LED signals emit light in a twenty degree (20°) cone in all directions (incandescent bulbs use a 40° cone). This makes it absolutely imperative that the signal heads be in proper horizontal and vertical alignment. It is for this reason that LED signal heads should not be used on roadways with extreme grades or extreme horizontal curvature. 

Any signals on span wires must be tethered at the bottom and a visual check of the signal head alignment must be performed in order to verify there is no negative impact on the traveling public.

The Manual on Uniform Traffic Control Devices (MUTCD) indicates that for an 85th percentile speed of 35 mph you would need to see the signal head from 325 feet away. If there are signals in your municipality, the MaineDOT asks that you take corrective action on any non-tethered or non-aligned LED signals. 

If you have any questions on this matter, please feel free to contact the MaineDOT Traffic Engineer at 624-3600.

Do You Have a Traffic Signal in Town?

New L.E.D. technology can dramatically cut your electric bill. The future of traffic signals is changing. Light emitting diodes (LED) are becoming an attractive alternative to standard incandescent lamps. Energy costs in several Maine communities have been significantly reduced by the installation of LED bulbs.

Although the initial cost of purchasing and installing LED's in traffic signals is relatively high, the long-term cost savings makes them an economical alternative. LED light fixtures have a life expectancy of ten years, compared with the one-year life expectancy of standard incandescent bulbs. 

The major advantage of LED's is a dramatic reduction in power consumption resulting in reduced energy costs. The city of Lewiston realized a 66% reduction in electrical costs from a typical intersection after installing LED's. The following chart, provided by Chris Branch, Public Works Director/City Engineer for Lewiston, summarizes Lewiston's savings for ONE of their intersections, before and after the installation of red LED bulbs in their traffic signals. 

Types of Bulbs
Number of Days
Kilowatt hours used
Kilowatt hours used per day
Incandescent
157
1763
11.2
LED
275
527
1.9

 

The Town of Yarmouth has replaced all of their red stop signals with LED's resulting in a 31% reduction in power usage. The following chart shows Yarmouth's actual energy savings for four signalized intersections. These numbers are for typical red-yellow-green assemblies with a total of 39 red bulbs replaced. 

 

Type
Estimated Annual Energy Savings
Number of Lamps
Cost for LED Lamps
Payback in Years
Red Flashers
$2,104
44
$11,680
5.6
Red Signal
$13,576
268
$64,320
4.7
TOTAL
$15,680
312
$76,000
4.9

 

Public Works Administrator for the Town of Yarmouth, provided the following information concerning their use of LED light fixtures:

  • LED lamp life is guaranteed for 7 years with replacement, if the bulb should fail. The LED lamp has a life expectancy of 10 years, which significantly reduces the number of bulb changes and therefore, the number of work zones required for these operations. This reduces work zone liability and costs associated with traffic signal maintenance.
  • Using 1995/1996 dollars, the LED bulbs have a payback period of 3-9 years. However, as power costs increase, the payback period will be reduced. At $.15 per kwh, a three year payback period can be expected.
  • Yarmouth's intersections have only red LED's installed. The walk lights, information signs, green and yellow bulbs also draw significant energy. As the other lamps are replaced with LED's, power consumption will be further reduced. In addition, costs will decrease and the need for annual bulb replacement will be eliminated.

It is obvious that significant cost savings can be realized through the installation of LED lamps. Currently, red, amber, and green LED lamps are available. Additional information regarding LED lamp replacement can be obtained by contacting Pete at the Center, Bill Shane in Yarmouth, Chris Branch in Lewiston, or MaineDOT's Traffic Engineering Section at 624-3600.

Why Consider LED's

  • Saves dramatically on power usage.
  • Eliminates bulb replacement for at least 7 years.
  • Reduces liability by reducing number of dead bulb changes, fewer work zones and less traffic disruption.
  • Low maintenance
  • No wire filaments
  • Not sensitive to mechanical shock and vibration
  • Visible and bright in all weather conditions
  • Available in all three colors
  • Pedestrian heads are now available

 

This page last updated on 1/9/13