Road Engineering Journal
Copyright © 1997 by TranSafety, Inc.
November 1, 1997
Fax: (360) 335-6402
It has been long recognized that those who design highways have given inadequate consideration to the maintenance problems that are related to many designs. Aging facilities, greatly increased traffic volumes, tighter budgets, and limitations on staff have only served to compound the problems associated with maintenance. The National Highway Research Program (NCHRP) Project 14-9 (2) was initiated in response to the need to develop a routine process to improve communications between designers and maintenance personnel during the design process. The obvious goal would be to minimize the impacts on maintenance over the expected life of the facility. NCHRP Report 349 "Maintenance Considerations in Highway Design" presents the results of this research project.
Part of this report addresses highway design features, including policies, roadways, drainage systems, appurtenances, and roadside elements. The specific maintenance problems related to these features and suggested solutions to these problems are summarized here. It is important to note that these recommendations have been reached through a research approach that included literature review, a survey of practices, interviews with selected state transportation agencies, and, in some cases, demonstrations.
In incorporating any of these suggestions or designs, agencies must first consider safety laws, regulations, guidelines, and any other design requirements in effect. The processes described here should serve as guidelines for individual jurisdictions and at the very least provide for better communication between design and maintenance personnel. (NCHRP Report 349 contains more detailed explanations of the various recommendations listed and also provides a summary of the participating states' responses to the questionnaires concerning maintenance and road design.)
According to Report 349, consideration of maintenance should begin early, during the location studies, and continue throughout the design process. Highway geometrics have a substantial impact on maintenance requirements. Erosion control, which generates a large portion of maintenance expenditures, can be minimized by proper location and geometric design. Access and right-of-way availability also contribute to ease of maintenance. In any case, policy should include the following design considerations:
Roadway features include mainline and ramp pavements, shoulders, medians, islands, and embankments. Since pavement maintenance and rehabilitation consume a large part of maintenance expenditures, roadway designs should incorporate the following considerations:
Maintenance problems related to drainage are costly expenditures. Constant attention must be given to controlling erosion in ditches, cleaning culverts and stormwater systems, repairing eroded and scoured outlet areas, controlling corrosion, and repairing damage due to frost and clogging. In planning drainage systems, designers should consider the following strategies:
Appurtenances also demand a large share of the maintenance budget. Traffic, vandalism, animals, and atmospheric conditions cause the most damage to these elements. Their maintenance and repair are labor-intensive. Substantial cost can be saved if they are designed and built to be safe, durable, and easy to maintain.
Appurtenances can be classified into two main categories: roadway appurtenances which include barriers and guardrails, glarescreens, pavement markings and markers, rumblestrips, and attenuators and roadside appurtenances which include signs, lights, delineators, sound walls, and fences.
The best way to design a highway is with minimal need for barriers and guardrails. Several other options can be used to protect vehicles in run-off-the-road situations:
Because pavement markings and markers wear from traffic, snow plows, sanding, and atmospheric conditions, maintenance is constant and, therefore, costly. Many jurisdictions recommend the use of epoxy, thermoplastic material, or precut tape in place of paint. Standard paint may be cheaper initially, but it does not withstand heavy traffic and harsh weather conditions. Raised pavement markers provide good visibility and have a long life span in non-snow areas. A grooved system with recessed pavement markings can be used in snow-plow areas. In some situations, depressed rumblestrips should be considered in place of raised markers.
Attenuators are used in places where hazardous fixed objects cannot be avoided-- such as bridge abutments, bridge rails, and sign posts. An ideal attenuator is durable and can easily be brought back to its original condition and position with inexpensive and available replacement parts. Consider the needs of snow removal and storage when using an attenuator, and make sure it does not create a hazardous condition on the adjacent lanes immediately following a collision.
Roadside appurtenances should be placed with maintenance access availability. Major maintenance requirements include painting, cleaning, replacing, and servicing fixtures of lighted signs and repairing or replacing support posts damaged by crashes or deterioration. Vandalism is a serious problem and demands serious maintenance efforts. Locate signs so that guardrail requirements are minimized, access is easily and safely available, visibility is not inhibited, conflict with landscaping and other highway elements is avoided, and vegetation control operations are not hampered.
Lighting improves visibility at night and thus greatly contributes to traffic safety. Maintenance requirements include cleaning, relamping, repairs, and replacement. Sound walls and fences provide for protection and improve maintenance, but both require repair or replacement due to vehicular crashes, deterioration, vandalism, rock slides, etc. Roadside maintenance problems include managing vegetation growth by mowing or chemical application, collecting debris and litter, minimizing the adverse effects of deicing chemicals on turf and trees, controlling erosion, and repairing the results of vandalism.
Although "maintainability" should have a high priority, the goal in highway design is to reduce the costs of maintenance and construction and to obtain the maximum benefit from highway expenditures at the minimum cost over the expected life of the project. Of course, the drivers who use the roads cannot be ignored. The impact of these operations on the highway user is critical, and highway maintenance processes must accommodate the ever-present effect of traffic. In every maintenance situation, safety and accessibility are important considerations for everyone involved.
Copyright © 1997 by TranSafety, Inc.