Bicycle Safety Guide and Countermeasure Selection System


Placing rumble strips on the left-most edge of the shoulder maximizes the ride-able space for bicyclists. - Bob Boyce - Austin Brown Constructing a paved shoulder. - Austin Brown




Paved Shoulders

Similar to bike lanes, paved shoulders provide separated space for the operation of bicycles. However, unlike bike lanes, paved shoulders are not considered travel lanes, and therefore may be used for temporary storage of disabled vehicles and vehicle parking, unless prohibited. Shoulder widths are typically a function of the amount of bicycle usage, motor vehicle speeds, topography, 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 and the AASHTO Guide for the Development of Bicycle Facilities. 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.

Rumble strips are often used as an inexpensive and effective countermeasure to reduce run-off-road crashes for motorists; however, installing rumble strips on a narrow shoulder causes bicyclists to have to ride in the travel lane rather than on the shoulder. If there is still rideable space on the shoulder, bicyclists may also have difficulty traversing the rumble strips without falling. Due to these issues, it is recommended that when rumble strips are installed, that four feet of useable shoulder space remains for bicycle travel. Placing periodic gaps in the rumble strips allows for bicyclists to safely move between the shoulder and travel lane. Alternate rumble strip designs that reduce the width, depth, or proximity to the travel lane should also be considered. The edge line may be painted on top of the rumble strip, which can reduce the impact on the adjacent shoulder while providing the additional advantage of increasing the visibility of the edge line at night. Given the safety benefits for motor vehicles, rumble strips should be considered at locations with a demonstrated run-off-road crash risk, but should be designed to minimize the risk to bicyclists.


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.


  • 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.

Estimated Cost

Costs vary, but it is most efficient to provide paved shoulders during street construction or reconstruction.


To view references for this countermeasure group click here.

Case Studies