Roadways: Shoulder Width

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ShoulderThe portion of the roadbed contiguous with the traveled way for accommodation of stopped vehicles, for emergency use, and for lateral support of base and surface courses. Width

Primary Guidance

  • Interstate shoulders:
    • Are required and shall be paved
    • 4 ft. to 10 ft. wide
    • Based on number of lanes and terrain
  • Rural and urban arterial shoulders:
    • Are desirable and should be provided
    • Widths range from 4 ft. to 10 ft.
    • Can be paved or graded depending on the function they provide and the constraints that are present
  • When graded shoulders are provided, a minimum 2 ft. of paved shoulder should be provided for maintenance, structural, and safety concerns
  • When bicycles are allowed on the roadway, the accommodation should be provided within the shoulder in accordance with MDOT approved Bicycle Policy
  • When minimum shoulder widths cannot be accommodated, a design exception and/or bicycle waiver may be required

Discussion

A shoulder is the portion of the roadway contiguous to the traveled way that accommodates stopped vehicles, emergency use, and provides lateral support of the subbase, base, and pavement. Shoulders may be paved with concrete or asphalt or unpaved with aggregate or soil.

When shoulders are provided, a vehicle stopped on the shoulder should clear the edge of the traveled way by at least 1 ft. and preferably by 2 ft. When roadside barriers, walls, or other vertical elements are present, the shoulder provided should be wide enough to ensure the vertical element is offset 2 ft. from the edge of the useable shoulder. This is also true when guardrail is placed along the roadway.

Regardless of the width, a shoulder functions best when it is continuous. The full shoulder benefits are not realized unless it provides a driver with refuge at any point along the traveled way. A continuous shoulder provides a sense of security so all drivers making emergency stops will leave the traveled way. Although continuous shoulders are preferred, narrow shoulders and intermittent shoulders are still superior to no shoulders at all.

Interstate shoulders will be paved and will be based on the following:

  • Level or Rolling terrain

2 lanes: left shoulder 4 ft. min, right shoulder 10 ft. min 3 or more lanes: left shoulder 10 ft. min, right shoulder 10 ft. min

  • Mountainous terrain

2 or 3 lanes: left shoulder 4 ft. min, right shoulder 8 ft. min 4 or more lanes: left shoulder 8 ft. min, right shoulder 8 ft. min

See Also