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.
Paved shoulders create separated space for bicyclists and also provide motor vehicle safety benefits and space for inoperable vehicles to pull out of the travel lane.
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- Provide a smoothly paved surface and keep free of debris. Where chip or slurry seal is applied to the roadway, Type II aggregate or microsurfacing may be used in the shoulder area to provide a smoother bicycling surface.
- 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. On uncurbed cross sections paved shoulders should be at least 4 ft wide and at least 5 ft in width should be provided if there are vertical obstructions immediately adjacent to the roadway.
- Provide rideable space for bicyclists if rumble strips are used.
- Where paved shoulders are present, accommodations should be made for bicyclists through the intersection. If shoulders are dropped at the intersection approach to provide for a right turn lane, signage should be used to indicate to motorists to expect bicycles and share the road. Parking should be restricted within the functional area of the intersection.
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Costs vary, but it is most efficient to provide paved shoulders during street construction or reconstruction.
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