Accommodating All Users
Safe accommodation of all road users can be considered when designing and applying rumble strips. Rumble strips are primarily a safety device for passenger vehicles. For other road users, particularly bicyclists, they may cause concerns. A part of the success in accommodating the variety of road users present on our roadways is the use of flexibility in the design and placement of rumble strips.
To fulfill their purpose, tires must drop into the rumble and cause enough vibration or noise inside the vehicle to get the driver's attention. There are opportunities to reduce the impacts of rumble strips on other road users by adjusting dimensions and location. This section explores information about how to accommodate all road users with effective rumble strip design and implementation. Coordination with local bicycling organizations is highly recommended when developing policies and projects.
Bicyclists, in particular, are affected by edge line and shoulder rumble strips. A few keys to consider are:
- Where shoulders are available and clear of debris, bicyclists will often choose to use them to avoid conflicts with faster moving vehicles in the travel lane; however, as legal road users, they may also be in the travel lane. There are a number of measures that can be considered to accommodate bicyclists.
- Recurring short gaps can be designed in the continuous rumble strip pattern to allow for ease of movement of bicyclists from one side of the rumble to the other. A typical pattern is gaps of 10 to 12 feet between 40- to 60-foot-long sections of the milled-in elements.
- Offset of the rumble strip from the lane can be adjusted to best accommodate bicyclists. This may mean using edge line rumble strips to provide additional paved shoulder space beyond the rumble strip, or increasing the offset where very narrow paved shoulders exist, to give the bicyclist additional space near the edge of the lane.
- Agencies often maintain 14 feet of pavement beyond the edge of the center line rumble where vehicles and bicycles are expected to share the lane due to a concern that motorists will shy away from center line rumble strips. Field studies indicate that center line rumble strips on two-lane undivided roadways with lane widths as narrow as 10 feet do not adversely impact the lateral placement of the vehicle in the travel lane.
- Bicyclists rarely need to cross a center line rumble strip, however, agencies often maintain 14 feet of pavement beyond the edge of the center line rumble where vehicles and bicycles are expected to share the lane due to a concern that motorists will shy away from center line rumble strips. Field studies indicate that center line rumble strips on two-lane undivided roadways with lane widths as narrow as 10 feet do not adversely impact the lateral placement of the vehicle in the travel lane.
Additional information related to accommodating bicyclists is contained in the following documents:
- Rumble Strip Implementation Fact Sheet: Bicyclists. This fact sheet is intended to provide general information on this topic to anyone involved in a rumble strip project.
- Rumble Strip Implementation Guide: Addressing Bicycle Accommodation on Two-Lane Roads . This guide is intended for planners, designers and safety professionals involved in the development of project-specific implementation of rumble strips or development of standards.
- FHWA Technical Advisory on Shoulder and Edge Line Rumble Strips (T 5040.39, Revision 1)
- FHWA Technical Advisory on Center Line Rumble Strips (T 5040.40, Revision 1)
Although studies indicate that center line rumble strips used in passing zones do not inhibit motorcyclists from passing, awareness of the rumbles strip by the motorcyclist is important. The MUTCD includes warning signs and plaques specifically for motorcyclists which may be appropriate in some locations. The following contain information related to the effects of rumble strips on motorcyclists:
- Rumble on Roads: The Sound of Safety – is a video produced by the North Dakota DOT in 2011 that provides an overview of the benefits of rumble strips to all road users. It also includes an interview with a representative of North Dakota American Bikers Aimed Towards Education (ABATE) supporting rumble strips as a safety countermeasure for motorcyclists.
- NCHRP Report 641: Guidance for the Design and Application of Shoulder and Center Line-Line Rumble Strips – This 2009 report examines the design and application of shoulder and center line rumble strips as a crash reduction measure, while minimizing adverse effects for motorcyclists, bicyclists, and nearby residents.
- Effects of Center Line Rumble Strips on Non-Conventional Vehicles – Published January 2008 by the Minnesota Department of Transportation
Where corridors carry a significant volume of truck traffic, designers can take into account both the applicability of the warning properties of rumble strips to trucks, and the appropriate placement within the pavement cross-section.
- Due to the larger tires on trucks, to alert a truck driver crossing the center or edge line, the length, width, and depth are critical and can not be reduced.
- In curvilinear alignment the potential for off-tracking can be considered. Increasing the offset of shoulder rumble strips may be appropriate in curves.
- In segments with both center line and edge line (or shoulder) rumble strips, the distance between the two sets of rumble strips can be considered carefully.