Maintenance Considerations in Highway Design

Highway DesignThe future maintenance of a facility cannot be overemphasized in highway project design. Projects which are difficult or costly to maintain, or those which require frequent maintenance activities, must be considered poorly designed.

Different highway projects and different areas can be expected to have different maintenance considerations. Reduced or low maintenance designs with limited worker exposure should be the ultimate goal. In addition to a maintenance perspective review during project design, the development of a specific list of design practices may be appropriate to address maintenance needs in a particular area. Such a list might
include the following:

  • Acquire drainage easements when necessary to grade outfalls and thus provide adequate drainage. Avoid instances where adjacent property elevation is well above the drainage outfall as this may form a dam at the outfall to the structure.
  • Where practical, try to match the drainage structure to the natural grade of the drainage channel, and then profile the roadway over the structure. This practice may reduce siltation in the structure and erosion at the outfall.
  • Avoid placing signs in the ditch. Such placement may impede drainage (making mowing more difficult) and result in erosion or siltation around the sign support. Where practical, riprap mow strips around sign supports may minimize the need for herbicidal treatment.
  • At exit gores, try to extend the riprap area to include any EXIT sign supports. Extending the riprap will eliminate the need to mow or hand trim around the sign supports and keep mowers further from traffic.
  • Address access control variations (perhaps due to changes in property ownership) at ramp gores during design.
  • Avoid the use of roadside barriers if the fixed object (culvert, large sign, steep slope, etc.) can be appropriately relocated or eliminated. The barrier itself represents a fixed object and should only be used where alternatives are impractical.
  • When designing grade separations, consider extending riprap on the header banks of the overpasses all the way to the cross road pavement. This eliminates the need to mow or maintain a small strip of soil under the structure.
  • Consider the provision of a narrow mow strip at the bottom or top of retaining walls to simplify mowing operations along the wall. Riprap considerations may also be appropriate in other locations (sign structures, narrow borders, etc.).
  • Generally, designs should reduce the amount of hand trimming that would be required and eliminate the places that are relatively difficult for mowers to access.
  • Provide access to areas requiring maintenance (mowing, bridge inspection, etc.).

To the extent practical, utilization of desirable highway design criteria recommended herein regarding maximum roadway sideslope ratios and ditch profile grades will reduce maintenance and make required maintenance operation easier to accomplish.