Introduction

Whether you are a visitor to Midland or a resident, you may have noticed some differences in the city’s traffic signal operations. Most traffic lights are brighter and easier to view than before, even when the sun is shining on them. That's because the City of Midland has installed Light Emitting Diode (LED) traffic lights in place of pre-existing incandescent lights.

Compared to incandescent traffic lights, LEDs have greater light intensity and are designed to absorb, not reflect, most sunlight that enters the lenses. Also, LED lights are more visible, last much longer, and use much less energy.

Various forms of LEDs have been in use in the U.S. for many years. Most of the tiny red and green indicator lights you notice on your appliances, radios, and other digital visual effects are LEDs. However, in the last decade, their use has expanded to many other areas, including use in automotive tail lights and turns signals, as well as traffic signals.

For several years, the City of Midland monitored the development of LEDs as an alternative means for street signal operation. Since LEDs require much less energy to operate, they cost less to operate.

Until recently, LED traffic light implementation was not an economically sound investment due to operations and reliability concerns as well as high costs for materials. However, technology has changed significantly in recent years, making LED light implementation an economical possibility for the City.

The City reviews signal operations annually and determines necessary upgrades to Midland's signal system. During one of these reviews, it was determined that many of the City traffic signal components (see photos at right) were scheduled for upgrade or replacement. To save on installation costs, LED traffic light implementation was considered as part of the traffic signal upgrade or replacement program.

The City of Midland also consulted with several Michigan municipalities that use LED traffic lights and determined that these lights have become very reliable considering the various climate changes in the state.

Efficiency of LED vs. Incandescent Lights

The basic mechanics of how LEDs create light are very different than that of incandescent lights used in traditional traffic signal operations. As described below, efficiency can be measured by the amount of useable energy.

Efficiency of Incandescent Lights

A standard light bulb relies upon electrically heating an element to emit visible light. Light emission requires a significant amount of power to occur. This process is called incandescence. Approximately 2% of the emitted energy from an incandescent source is useable visible light with the remaining 98% being wasted heat. Incandescent bulbs are likely to burn out frequently and require replacement each year.

Efficiency of LED Lights

In contrast, LEDs are much more efficient and last longer. That’s because LEDs emit light by using an electrical current to create a bond between positive and negative charges. This process is called electroluminescence. This is much more efficient, as nearly 100% of the emitted energy from an LED source is useable visible light. Due to varying energy use, LED traffic lights are known to last approximately 10 times longer than incandescent traffic lights. LED traffic lights usually have a replacement warranty of five years, but are expected to last longer.

Standard incandescent light is diffused light, which basically means the light spreads out when in operation. Standard LEDs produce direct light but can be manipulated to diffuse, or spread out, so the light is visible at different angles. This can be controlled by altering the size, shape and location of some of the LED components that make up an LED traffic light.

Researching LED Costs

When determining costs of LED implementation, the City of Midland utilized Michigan Department of Transportation (MDOT) research regarding acceptable LED traffic light products in Michigan. Acceptable products must meet State standards regarding light intensity and reliability, among other things.

Cost of LED vs. Incandescent Lights

When looking at cost comparisons between incandescent and LED lights, the City considered three main factors: costs for materials, energy use, and labor.

Material Costs:  This includes all signal components required for LED or incandescent traffic light installation. Up front costs for LED traffic light materials are substantially higher than incandescent traffic light materials.

Energy Costs:  Energy costs for LED traffic lights are considerably less than costs for incandescent traffic light materials.

Labor Costs:  Labor and equipment to material assembly and installation are necessary costs. When comparing labor costs between qualified City of Midland staff and private contractors, it was found that installation by City staff in a five-year period would cost less than contracting out the work.

Considering the LED/incandescent comparison of materials, energy and labor costs, it was determined that the new LED system will pay for itself in approximately four years. As indicated in the table below, it will cost the City less to replace lights with LED materials than it would to replace traffic lights made with incandescent materials.

Table 1: Total Installation and Operating Costs - LED vs. Incandescent Lights

The table below shows the estimated total savings for using LED lights when comparing the installation and operations costs between LED and incandescent lights.

Table 2: Comparison of Installation and Operating Savings Using LEDs vs. Incandescent Lights

Installation of the new LED lights took about five years. By spreading the implementation over that time span, City staff has been able to balance LED light maintenance and replacement with their regular operations.

After five years, the LED warranty expires; therefore LED replacements will occur in five-year increments.

In order to develop and balance the work necessary for a five-year LED installation plan, City staff considered:

• signalized intersection locations,

• type of LED traffic light installation needed,

• the amount of time required for each signalized intersection installation,

• funding, and

• time of day, month and year for performing the work

In Midland, there are various types of LED traffic light installations to consider when scheduling the work:

1. Type I, LED Inserts LED inserts, or fixtures, can be placed in newer existing incandescent signal heads at the intersection location. However, only newer signal heads that can convert from incandescent to LED lights will be changed. Completing the work on site saves time by avoiding assembly in the shop using new signal head components.
2. Type II, Shop Assembly for Mast Arm Install Work involves building and installing new signal heads with LED inserts and mast arm components. Mast arms are rigid horizontal posts to which signal heads are attached. This type of work requires assembly in the City's Signal Shop.
3. Type III, Shop Assembly for Span Wire Install Related work involves building and installing two-way, three-way or four-way signal heads with wiring for span wire connections. This type of work requires assembly in the City's Signal Shop.
4. Type IV, Pedestrian LED Install Pedestrian LEDs are assembled at the Signal Shop. Installation is time-consuming since LED pedestrian signals are unlike pre-existing incandescent lights. Field modification of the bracket assembly is required.

Reduction in Energy Costs

To Find Out More...

For more information regarding LED lights, contact the City of Midland Engineering Department at 989-837-3348, or send an e-mail to bmcmanus@midland-mi.org.