The unusual noise tires make as they cross over rumble strips keeps drivers alive–but it may also keep neighbors awake. To fulfill their purpose, rumble strips must make enough noise inside the vehicle and tires must drop into the rumble to cause enough vibration to get the driver's attention.
HOW SERIOUS IS THE NOISE PROBLEM?
The typical noise level inside a passenger vehicle without additional interior noise sources such as a radio playing is 60 decibels. It is not clear what combination of noise level increase and amount of vibration is necessary to alert a drowsy driver, but numbers from 6-15 decibels are mentioned in various studies. The increase in noise inside the passenger compartment typically correlates to an increase in noise outside the vehicle, which is why neighbors object to rumble strips. Proximity also greatly affects the amount of noise heard by neighbors.
Road agencies have experimented with several alternatives to reduce exterior noise. Some simply ban their use in residential areas, while others try other alternatives to improve safety before considering rumble strips. And when rumble strips are placed near residences, agencies may discontinue the rumble strips where residences are very close to the road or around tight curves where large vehicles are more likely to have a wheel go beyond the edge line. An alternative is to move the rumble strips farther away from the travel lane. However, the further the rumble strip is from the travel lane, the less effective the rumble strip will be in reducing crashes and it more likely to impact accommodation of bicyclists. For more information see Section 9 in NCHRP Report 641.
Other Considerations and Resources
- Rumble Strip Implementation Fact Sheet: Noise. 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 Noise Issues on Two-Lane Roads.This guide is intended for noise 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)