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SWUTC Research Project Description

The Impact of the Conversion of Incandescent Bulbs to LED Bulbs Traffic Signals in Houston: A Step toward Sustainable Control Devices

University:  Texas Southern University

Principal Investigator:
Khosro Godazi
Center for Transportation Training and Research
(713) 313-7925

Project Monitor:
Dan Lynch
Traffic Engineers, Inc.
Houston, TX

Funding Source:  USDOT

Total Project Cost: $70,000

Project Number:  600451-00041

Date Started: 10/1/12

Estimated Completion Date:  9/30/13

Project Summary

Project Abstract:
With the slowing of the American economy since 2008, it has become imperative that municipalities identify areas in which costs can be reduced while still providing needed services to its constituents. The use of Light Emitting Diode (LED) Traffic Signals provides an opportunity for the City of Houston to save both money and energy. With other advantages such as reduced need for maintenance, a longer life span, and more illumination than the standard incandescent light bulb, LED’s have become a viable option in cities around the globe as a first step in reducing costs. Furthermore, LED traffic signals could be retrofitted to solar energy in the future thereby enhancing the move towards “green” technologies.

Project Objectives:
The city of Houston has 2,450 intersections. By converting all of the intersections from Incandescent bulbs to Light Emitting Diodes the city will have the opportunity to take part in reducing the amount of money and energy it uses every year. This study will prove the following:

  • Advantages and disadvantages of using LED’s and solar energy in traffic signals;
  • A cost comparison for the total number of signals in the city based off of a mathematical simulation of 100W for Incandescent bulbs and 20W for LED bulbs; and
  • A proposed cost of materials and labor based off of quotes from a manufacturing company for the conversion of the incandescent traffic lights to LED traffic lights

With this evidence our aim is for City of Houston officials to agree and help come up with a way to get all signals converted.

Task Descriptions:
Task 1: Literature Review
The purpose of this task is to do a literature search and identify the findings from best practices in some other countries and U.S related to this project.

Task 2: Cost related with Incandescent bulbs vs. LED and Savings
Create a matrix identifying costs related to LED traffic lights versus traffic lights with incandescent bulbs and the labor required to perform retrofit installation.

Task 3: Power Consumption and Energy Savings
Observe and collect data from actual meter readings for 10 intersections for LED traffic lights and incandescent traffic lights for a period of four months. Each observed intersection will have four approaches with six lenses per approach (2 red, 2 green, 2 yellow, and 2 pedestrian heads) per street, which is typical of most intersections in Houston.

Task 4: Operational Characteristics
The purpose of this task is to examine and observe the visibility and energy consumption of LED traffic lights in various weather environments and estimate the life span of the LEDs as well as the life span of the reserve battery.

Task 5: Final Report
The purpose of this task is to document all the information and data that has been collected and submit it as final report for SWUTC.

Implementation of Research Outcomes:
This study examined multiple scenarios of incandescent versus LED light sources. A simulation is presented based upon previously calculated costs, power consumption data, and installation costs. These variables provide a base line for the retrofit of existing incandescent traffic controls to an LED based light source and the associated costs of each intersection.

Products developed by this research:

Publication:  Traffic Sunlights:  Houston Takes a Hard Look at Solar-Powered Devices, Khosro Godazi, published in Roads and Bridges, January 2013.

Impacts/Benefits of Implementation:
The use of traffic signals equipped with light emitting diodes (LED) provides opportunities for urban municipalities to conserve both tax dollars and energy. With other advantages, such as the reduced maintenance, a longer life span, and more illumination than the standard incandescent light bulb, LED’s have become a viable option in cities around the globe as a first step in reducing municipal costs.

Web Links:
Roads and Bridges Article
Final Technical Report