Applicable Countermeasures

Paved Shoulders

Paved shoulders are very similar to bike lanes as a bicycle facility. The pavement edge line for the paved shoulder provides separated space for the bicyclist much like a bike lane. Depending on the situation, the width of the shoulders may vary. If the paved shoulder is less than 1.2 m (4 ft) in width it should not be designated or marked as a bicycle facility. Widths are typically a function of amount of bicycle usage, motor vehicle speeds, percentage of truck and bus traffic, etc., although widths are sometimes purely a function of available right-of-way. More paved shoulder design details are given in the AASHTO Green Book.5 Prior research has shown that paved shoulders tend to result in fewer erratic motor vehicle driver maneuvers, more predictable bicyclist riding behavior and enhanced comfort levels for both motorists and bicyclists.3

Colored shoulders have been used in Europe to visually narrow the roadway. This technique has been tried in Tavares, FL, where a section of roadway added painted red shoulders (see case study #14). The intent was to provide increased room and comfort for walkers and bicyclists. The 0.6 km (1 mi) treated section of roadway was a two-lane rural roadway with approximately 1,700 vehicles per day and had a 56 km/h (35 mi/h) speed limit. Even after the roadway was widened, the use of the red shoulders resulted in motor vehicle speeds similar to the before (narrower roadway) situation.6

Broward County, FL, has experimented with another paved shoulder variation. Undesignated lanes 0.9 m (3 ft) have been implemented on a number of roadways which formerly had wide 4.3 m (14 ft) curb lanes in place (i.e., 3.4 m (11 ft) travel lane and 0.9 m (3 ft) undesignated lane). The lanes were left as undesignated because they were too narrow to be referred to as bike lanes. The striping resulted in a delineated, although sub-standard, space for bicyclists to operate on these roadways (see case study #15).7

Rumble strips are often used on shoulders to alert sleepy or inattentive motorists, but there is considerable debate about what kinds of designs are safe or appropriate for bicycles. AASHTO recommends that 1.2 m (4 ft) of ride-able surface should be present for bicyclists if rumble strips are used on a shoulder.


  • Create travel facilities for bicyclists.
  • Create separated space for bicyclists.
  • Reduce or prevent the problems associated with bicyclists overtaking motor vehicles in narrow, congested areas.

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  • Provide adequate width by taking into account factors such as the amount of bicycle usage, motor vehicle speeds, percentage of truck and bus traffic, etc.
  • Provide ride-able space for bicyclists if rumble strips are used.
  • Examine alternative space for bicyclists if there are intersecting side streets.
  • Provide a smoothly paved surface and keep free of debris.

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Estimated Cost

Paved shoulder costs can be quite variable. Using data from Iowa DOT average contract prices for calendar year 2000, a minimum design width of 1.2 m (4 ft) of paved shoulder width to accommodate bicycle traffic was estimated at $44,000 per km ($71,000 per mi).8

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Case Studies

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