Paved shoulders

A clear and wide shoulder provides an attractive bicycle facility in this rural area.

The AASHTO Guide for the Development of Bicycle Facilities notes that in rural areas "adding or improving paved shoulders often can be the best way to accommodate bicyclists" and they have the additional attraction of providing a variety of benefits to motorists and other road users as well.

Critical dimensions

  • Less than 4 feet (1.2m): any additional width of paved shoulder is better than none at all, but below 4 feet a shoulder should not be designated or marked as a bicycle facility.
  • 4 feet (1.2m): minimum width to accommodate bicycle travel. This measurement should be the useable width and should NOT include the gutter pan or any area treated with rumble strips
  • 5 feet (1.5m) or more: minimum width recommended from the face of a guardrail, curb or other barrier

Widths should be increased if there are higher levels of bicycle usage, motor vehicle speeds are above 50 mph, or there is a higher percentage of truck and bus traffic. Further guidance on the appropriate width of shoulders to accommodate bicyclists on roadways in these situations can be found in FHWA's Selecting Roadway Design Treatments to Accommodate Bicyclists.

Critical issues and Frequently Asked Questions

When should I designate a shoulder as a bikeway?

Paved shoulders, whether they are designated and signed as bikeways or not, provide a great place for people to ride. Most states do not designate or mark their paved shoulders as bikeways, but some do, such as Oregon. Paved shoulders should not be designated or marked as bikeways unless they meet the width guidelines shown above (4 feet or 5 feet from a barrier or railing) and have rideable width free from obstructions or treatments such as rumble strips (see below). Oregon usually designates shoulder bikeways if they are a minimum of six feet wide, while Florida sets five feet as their minimum.

Designating a shoulder as a bikeway may also be useful to provide guidance to cyclists following a particular route (e.g. between two trails, or other popular destinations for bicyclists). The advice on signed shared roadways should be followed.

I have heard that the installation of rumble strips on paved shoulders is an issue. How can it be resolved?

There's no question that rumble strips are effective in alerting sleepy or inattentive drivers and that their use has positive safety benefits. However, it's equally true that none of the current designs for rumble strips can be considered "bicycle safe" and that the use of rumble strips can render a shoulder unusable for bicycling. The AASHTO bicycle guide recommends that rumble strips not be used on routes used by bicyclists unless a minimum of four feet of rideable surface remains for the bicyclist (five feet from a curb or guardrail). Other policies that have balanced the needs of motorists and bicyclists include:

  • using rumble strips exclusively on limited access or controlled access facilities
  • using a textured white fog line (Oregon) rather than rumble strips
  • leaving gaps (12 feet in every 60 feet) between the rumbles to allow bicyclists to cross them if necessary

For more information on rumble strips visit FHWA's resource site or learn about a bicycle user group's perspective.

Example

Wisconsin DOT has a policy of providing a three foot paved shoulder on all highways with an average daily traffic in excess of 1,000 vehicles, and this is widened to five feet if a moderate number of bicyclists regularly use the road. See page 38 of the WisDOT State Bicycle Plan.