U.S. Department of Transportation
Federal Highway Administration
1200 New Jersey Avenue, SE
Washington, DC 20590
Vehicles and cyclists have shared our nation's highways for some time. As the volume of each increases, the conflicts between the two modes of travel also increases. State highway agencies currently installing rumble strips are aware of the concerns and problems shoulder rumble strips pose for the bicycle traveler. These agencies are also aware of the great benefit this safety treatment provides in reducing the number of run-off-road crashes, many of which often result in fatalities and/or serious injuries. Over half of our country's traffic fatalities are caused by roadway departure crashes. Many of these crashes are attributed to drowsy or inattentive drivers. Studies show that the presence of shoulder rumble strips can reduce the number of such crashes. Most agencies are working to find solutions to the identified problems for the cyclists and still be able use this highly effective safety treatment.
Bicycles are allowed on some freeways and expressways and on most primary and secondary roads. Many bicyclists prefer to ride on the shoulder, outside the travel lane and out of the truck and automobile traffic stream. One of bicyclists' main concerns about rumble strips is the ability to control the bicycle when the rider needs to travel across or along the rumble strip for such maneuvers as a left turn or to avoid debris or an obstacle on the paved shoulder. Travel to the right of the rumble strip is generally most beneficial for the bicyclist as long as that area is free of debris and obstacles and the travel path is wide enough to comfortably accommodate the bicycle.
Some highway agencies have instituted policies that prohibit the use of shoulder rumble strips on roads designated as bike routes or where there is insufficient remaining paved shoulder room to accommodate bicycle travel. Others evaluate the use of rumble strips on a case-by-case basis and often opt to install them only at locations with a history of run-off-road crashes.
Several options are being considered to address the concerns for the bicycle traveler. The selection of a particular shoulder rumble strip design or revisions to current designs may provide part of the solution. For example, milled shoulder rumble strips are narrow and usually require less space on the shoulder than other types of strips. The narrower width of the strip allows more shoulder room for the bicyclist to maneuver on the right side of the shoulder. Other designs being used and investigated use a skip pattern of rumble strip that provides a smoother travel path throughout portions of the strip for bicyclists to move to the left when needed. Also, some highway agencies are providing an aid to cyclists and all travelers in general by posting roadside signs, such as RUMBLE STRIPS AHEAD, alerting the traveler to the presence of the shoulder rumble strip.
The NCHRP has recently completed a project to study and recommend solutions that will address the needs of the bicycle traveler and the presence of shoulder rumble strips. The project included an extensive review of past research. Some research is also underway at universities to study the effects of installing a rumble strip along the center of the travel lane. Such an installation is seen as a way of alerting drowsy or inattentive drivers when they deviate from the travel way, where there is insufficient room on the shoulder to provide for the strip and the bicyclist or where the shoulder is unpaved. There is concern now about introducing a possible hazard in the travel way to motorcycle riders, especially those towing trailers, and to other drivers in general who may be unsafely distracted by the presence of an extended textured strip along the middle of their travel path.
Many highway agencies are working with their various constituencies to address the concerns and problems identified. One of the purposes of this Internet website is to provide a means of sharing information and experiences from around the country so all users can benefit from the ideas, knowledge, and experiences of others. We trust that through this effort all highway agencies will find a source of additional information to help in safely providing for the travel of all of our roadway users.