Web Extra

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Appropriately designed, operated, and maintained signals reduce congestion, improving mobility and air quality. But like all jurisdictions, we struggle to find a way to formalize preventive maintenance while responding to emergency calls and overcoming a ‘fix-it-when-it-breaks' mentality.

After analyzing the operations of the three elements of maintenance—emergency calls, preventive efforts, and shop repairs—we took the plunge and implemented a preventive maintenance plan in fall 2005. By the end of the year, we'd inspected, cleaned, and replaced worn components or 714 traffic signals, 74 intersection beacons, and 300 school flashers on 2,600 miles of road.

One year later, malfunctions — which consume up to an hour from when our control center receives a call to when a technician puts his unit back in service for the next call — had dropped 36%. That translates to 1,786 fewer hours of gridlock.

Malfunctions over the next year were a tad less impressive — down 29% from 2005 — but we attribute that to the 18 new signals that were added to our inventory. (One-third of the signals we maintain are on state routes and permitted by the state.) In 2008 malfunctions were slightly up from 2007, but they were still down 22% compared to the year before we implemented our preventive maintenance plan.

Technicians are identifying loop problems before they become emergency calls. They're replacing bulbs before they burn out. Checking and adjusting height is now on the maintenance checklist, so fewer low-hanging signal heads are being hit by trucks. Rodent bait, ant bait, and wasp spray are standard equipment for formerly infested control cabinets.

While there were some initial costs — mainly, warehousing larger quantities of stock items like controller filters, loop detectors, incandescent bulbs, and modems — there was no increase in labor cost. We handled the additional work by rearranging crews and modifying assignments.

Nor did we need additional vehicles. Because all maintenance is performed in-house, employees use their assigned bucket trucks, loop trucks, and pickup trucks.

As for the plan itself, virtually everything we needed to streamline the process was already in our hands; we just needed to review and standardize procedures.


Because all three maintenance elements are related to each other, we evaluated all three when attempting to standardize preventive maintenance:

Emergency maintenance. We have four technicians on duty from 7 a.m. until 11 p.m. every day, including holidays. Coupled with our in-house responding staff, our extended hours of operation were already providing the county with excellent emergency response.

Technicians were required to complete a pre-printed standardized report regarding the cause of a malfunction and the actions taken to make the repair. An analysis of this data showed we were responding quickly to emergencies while generating crucial historical data on the frequency and type of repairs eating into our overall productivity.

Preventive maintenance. With no clear set of objectives or finite set of activities to be performed as part of the preventive maintenance routine, technicians were free to determine which items would be a part of their maintenance checklist. With 15 technicians, we had 15 different maintenance objectives.

Some assets received regular preventive maintenance; others received none. Technicians tended to perform preventive activities only after responding to, and restoring operation at, a malfunctioning signal. But because malfunctions usually occur at the least opportune times — bad weather, rush hour — for such activities, signals didn't receive thorough analyses.

That's why we decided preventive maintenance would be performed as an independent primary activity instead of a rushed, haphazard afterthought.

Bench maintenance. Malfunctioning components were always returned to the shop for testing and repair.

We suspected that formal preventive maintenance would likely increase the number of components needing diagnostics and repair, thus increasing the workload for our bench repair technician; and we were right.

After the first year, repairs had increased by 30%. A second field technician was reassigned to help, and now we're saving money because more equipment is being reused instead of replaced.


After taking all of the above into account, we developed a checklist of preventive activities by reviewing maintenance reports to determine which major and minor signal components failed most often. While the list is comprehensive, technicians can fill it out quickly. (See “Web Extra” below to access a copy of the form.)

The next step was to rearrange the responsibilities of the two technicians whose primary assignment had been responding to emergencies as well as those of construction crews whose primary responsibility had been major signal construction and upgrades.

The third and final step was to implement the plan.

Now, almost four years into our program, the benefits have far outweighed the start-up costs of maintaining a larger inventory of equipment and traffic signal components.

Even better, the traveling public has noticed — and commented positively on — a more efficient signal system.

— Allen (404-294-2041, pvallen@co.dekalb.ga.us) is deputy director of traffic and safety engineering for DeKalb County, Ga.

Making the grade

National Transportation Operations Coalition tool helps departments focus resources.

Developed in 2005 and updated in 2007, the National Traffic Signal Report Card covers management, signal operations at individual intersections, signal operations in coordinated systems, signal timing practices, traffic monitoring and data collection, and maintenance.

“We decided to concentrate on maintenance because we felt we could get the greatest return for the smallest initial investment,” says Peggy Allen, deputy director of the Traffic Engineering Department of DeKalb County, Ga. “Also, with congestion a major concern for metropolitan Atlanta, of which DeKalb County is part, we wanted to see how an effective program would affect congestion.”

When the department formalized preventive maintenance in 2005, its self-assessment grade in the report card's maintenance category was one point lower than the national average of 67, and congestion was costing the region almost $2 billion annually.

The department calculates “cost of congestion” using data from the Texas Transportation Institute's Annual Urban Mobility Report. In 2005, according to the report, the per-person value of the extra time and fuel consumed by vehicles traveling at slower-than-allowed speeds was $14.60/hour; and metropolitan Atlanta commuters were spending 60 hours annually stalled in traffic.

Thus, that year traffic delay added $876 to the average commuter's travel costs.

Let's look at how a malfunction at one of DeKalb County's largest intersections — Peachtree Industrial Boulevard and the I-285 eastbound ramp (pictured above) — affects traffic flow. The former has annual average daily traffic (AADT) of 109,800 vehicles and a peak-hour volume of 5,916; the latter an AADT of 32,038 vehicles and a peak-hour volume of 1,783. A one-hour repair at this intersection creates $112,405.40 in congestion/delay costs.

By 2007 the department's maintenance grade was 78 — eight points above the national average — and commuters were avoiding millions in congestion costs. –Stephanie Johnston

Source: DeKalb County Traffic Engineering Department