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. Placing periodic gaps in the rumble strips allows for bicyclists to safely move between the shoulder and travel lane. 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.
- Shoulder width of at least five feet is recommended, but additional space should be provided on roads if there are higher levels of bicycle usage, if motor vehicle speeds exceed 50 mi/h, or if there is a higher percentage of truck and bus traffic.
- If the shoulder has rumble strips designed to alert swerving motorists, there should still be at least four feet of â€œrideableâ€� surface for bicyclists. Periodic gaps in the rumble strips should also be provided to allow bicyclists to travel across the rumble strip as needed.
- 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.
The cost varies, but often there are opportunities to include shoulder paving projects with resurfacing or reconstruction projects.