Road Management & Engineering Journal
February 2, 1998
(U.S. and Canada)
Fax: (360) 335-6402
|(This information is reprinted from the "National Cooperative Highway Research Program (NCHRP) Synthesis of Highway Practice 245: Traffic Control Systems, Maintenance Management Practices" by Walter H. Kraft. Reproduced here is the "Summary" from that document. The complete publication is available from TranSafety, Inc. for $21.00 plus $4.00 shipping and handling. It is 71 pages in length and was published in 1997.)|
Traffic control systems are expected to grow in size and complexity, even as resources continue to decrease. Many transportation agencies currently believe that they are doing a fair to poor job of maintaining their present systems. How, then, will agencies be able to improve the maintenance of their systems while doing more with less? One way is to use the best maintenance systems available that will suit their needs. This synthesis has been prepared to present the state of the practice in maintenance management of traffic signal control systems to assist agencies in improving their own systems.
Maintenance management practices vary widely among transportation agencies. Most agencies (50 percent of those answering a survey of 152 transportation agencies) use a paper filing system, even though there are many types of software available for management, scheduling, administration, inventory control, and record keeping. It is expected that more agencies than the 18 percent that reported using computerized system[s] will do so in the future.
Maintenance is divided into three types: response, preventive, and design modification. Response maintenance is performed on an as-needed basis to repair a malfunction and is practiced by all agencies with varying response times. Preventive maintenance is performed on a regularly scheduled basis using a set of procedures to preserve the intended working condition of the traffic control system. Most, but not all, agencies perform this type of maintenance, which represents about one-third of their overall program. Design modification is used to correct a recurring problem, to accommodate changes in prevailing traffic or physical conditions, or to update installations to the current state of the practice. Approximately 75 percent of the agencies surveyed reported design modification activities, which accounted for about one-sixth of their traffic signal control system maintenance program.
Most agencies do not share resources such as personnel, devices, equipment, responsibility, or authority with other agencies. They most often use the low-bid process for the procurement of equipment, parts, and service. In some cases a prequalifications process is added.
The number of maintenance personnel has changed over the years as a result of the evolution of traffic control equipment from mechanical to electronic devices. For those agencies that maintain their own systems, the survey revealed that the number of maintenance personnel generally increased with an increase in population at a rate of approximately 2.6 employees per 100,000 persons for city agencies and a rate of 2.3 for state agencies. No definable rates could be determined for agencies that contract all or part of their maintenance.
County agencies appeared to have larger budgets for equipment than states and cities, while state agencies appear to have the largest budgets for personnel and spare parts. Cities have the highest budget for contractor services. The source of budget funds is local and state taxes and gas taxes. The mix of taxes varies by government level and is expected to change in the future.
Tools are available to improve the maintenance management of traffic control systems to help agencies cope with an increase in the system size and components while facing reduced resources. The information in this synthesis can help agencies to understand these tools and improve their programs.