Solution Summary: Rumble Strips
Temporary rumble strips consist of several raised bars arranged along a traffic lane to create tangible physical vibrations and noise to alert drivers to impending obstacles. These are usually made of plastic/polymer (e.g., recycled rubber), a strong and durable material that won’t be damaged or diminished as traffic runs over it.
Transverse rumble strips run along the entire driving lane. These types of rumble strips are usually temporary, especially when used in a construction work zone. The ease of installing and removing rumble strips have made them practical for use in work zones. The American Traffic Safety Services Association has developed a guide for use of temporary rumble strips in work-zones and classified them into 5 types. The main features of each type are as follows: Preformed thermoplastic strips are easy to install as these pre-cut products can be placed regardless of the temperature of the road. Pavement Marking tapes could be placed on top of each other until reaching the desirable thickness. Adhesive strips are produced with an adhesive backing which makes the installation and removal process easier while manually adhesive products can be found in different colors to improve visual detection. The last type, portable reusable strips, are ideal for short-term work-zones. Table 1 provides more information about different types of rumble strips that can be used near work-zones and their installation and removal procedures.
Work zones near roadways could create various changes in road conditions that might be a surprise to drivers, such as unexpected change in alignment of lanes, a reduction in speed limits, a lane closing, new merge patterns, visual obstruction ahead, and even night-time work zones. Near work zones, inattentive drivers are exposed to the risk of hitting construction workers or equipment, resulting in injuries to the driver as well as construction workers. Rumble strips could be used to increase awareness of drivers regarding upcoming conditions, enabling them to reduce vehicle speed and follow the change in traffic due to a work zone.
How Risks are Reduced:
Vibration and noise can make drivers more alert, which in turn will significantly lower the chance of struck-by accidents near or in a work zone. Rumble strips can create enough vibration and noise in a moving vehicle to warn the driver to slow down, move over, or stop. While rumble strips do not deliver a specific message, they can alert drivers that conditions ahead are changing. Sun et al. (2011) revealed that temporary rumble strips increase braking by more than 10% and that the brake speed on average slows by 3.71 mph. They also found that speed compliance increased about 2.9% when strips were in use.
Effects on Productivity:
Rumble Strips have a very small effect on productivity. They are easy to install and remove and can be reused, as well.
Studies have shown that for greatest effectiveness, rumble strips need to be used together with other traffic control devices. This allows the rumble strips to do their main job of alerting drivers and bringing them to a high attention level so they can see a “caution sign” (e.g., slow speed ahead).
During this process, it is also important to think of the surroundings of the work zone to minimize disturbances to residents or businesses close to the work zone.
The following recommendations are provided by FHWA regarding the installation of rumble strips (Figure 2):
1. Rumble strips should be between 7mm and 13mm thick and should be in a set of six spaced a maximum of 2.7 meters apart. At 50 mph or less, it is recommended to have gaps of 1.8 meters to 2.4 meters between rumble strips. At speeds greater than 50 mph, rumble strips can be spread strips 2.1-2.7 meters apart. Regular spacing between the singular strips could seem to drivers like regular control joints in the pavement (Figure 3). Irregularity in spacing is necessary to eliminate that misconception and properly alert the driver. Higher speeds require wider spacing between sets to provide enough time for drivers to reduce speed and become aware of the upcoming work zone area.
2. Installation of temporary rumble strips should closely follow the department’s or manufacturer’s regulations/instructions, including details on air and pavement temperatures. If moisture is present in the air or on the pavement, cleaning of the pavement as well as choosing the proper adhesive are important.
3. Temporary rumble strips should be used only when necessary. If audible and tactile warnings need to be provided for the safety of the workers or drivers, then rumble strips are highly recommended. Possible situations include detours, splitting lanes, lanes turning into exit/turn only, single lane traffic, stop light ahead, abrupt reduction in speed limit, and other varying traffic patterns.
Figure 2. Example of setting up a set of temporary rumble strips. (FFWA-NJ-2013-002 Report)
Figure 3. A picture of temporary rumble strips before a work zone.
Behzad Esmaeili, Ph.D. - University of Nebraska- Lincoln
Pouya Gholizadeh - University of Nebraska- Lincoln
Sogand Hasanzadeh - University of Nebraska- Lincoln
Erik Bruening - University of Nebraska- Lincoln
Brett Farquhar - University of Nebraska- Lincoln
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