DOT&PF - Statewide Design & Engineering Services - D&CS - Traffic & Safety

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What are rumble strips?
How do shoulder rumble strips increase highway safety?
How do centerline rumble strips increase highway safety?
Why install rumble strips in Alaska?
What is the effect of shoulder rumble strips on bicyclists?
Why use centerline rumble strips in passing zones?
Are rumble strips safe for motorcyclists?
Do rumble strips cause noise problems for nearby residents?
Do rumble strips damage the pavement?
How do drivers react in locations where centerline rumble strips are used in passing zones?
How many states use centerline rumble strips and what is their combined experience?
Are rumble strips still effective in the winter?
What design criteria are Alaska DOT/PF using for Rumble Strip installation?

How do shoulder rumble strips increase highway safety?

Rumble strips on the shoulders reduce run-off-the-road crashes by warning drivers they are leaving their lane. They are located just beyond the white line or the traveled portion of the roadway. As of 2009, over 35 states use shoulder rumble strips on their roadways.

Two-Lane Two-Way Highway Performance

In Alaska, about 36 fatal crashes per year are due to run-off-the-road crashes on two lane roads. Shoulder rumble strips are one of the most cost-effective countermeasures for these crashes. A review of the performance of shoulder rumble strips installed since 2000 in Alaska shows a 22% decrease in fatal and injury crashes statewide. A 29% reduction was achieved in southcentral Alaska on roads with shoulder rumble strips. Statewide, over 5 lives and 17 serious injuries are estimated to have been prevented each year where rumble strips have remained in place.

Minnesota studied shoulder rumble strips on their two-lane two-way rural highways. They reported 40% of all 2004 fatal crashes were single-vehicle, run-off-the-road (SVROR) crashes. Milled-in continuous shoulder rumble strips were installed at 23 treatment sites (183 miles). The result was a 13% reduction in all SVROR crashes and an 18% reduction in injury-producing SVROR crashes after shoulder rumble strips.

Source: (Estimating Safety Benefits of Shoulder Rumble Strips on Two-Lane Rural Highways in Minnesota: Empirical Bayes Observational Before-and-After Study )

Freeway Performance

Alaska data from 2001 through 2006 was not conclusive enough to show any benefits due to the small segments of freeway which remain treated with shoulder rumble strips in Alaska. However, data from other states suggests they will be effective at reducing crashes in the long term. Alaska crash data demonstrates there is a crash problem even when roads are dry and uncongested.

California and Illinois data were combined from the Highway Safety Information System (HSIS) to estimate the safety effects of shoulder rumble strips on freeways. Before-after evaluations estimate single-vehicle run-off-the-road crashes were reduced on average by 18.3 percent on all freeways (no regard to urban/rural classification) and 21.1 percent on rural freeways. Two potential adverse effects related to safety were analyzed. The crash risk due to driver startle/panic responses and the potential for crash migration were explored. The research findings show these potential adverse effects are insignificant.

Source: Safety Evaluation of Continuous Shoulder Rumble Strips Installed on Freeways, December 1999, FHWA-RD-00-032

California performed a before-and-after study in 1985 which indicated a 49 percent reduction in run-off-road crashes after shoulder rumble strips were installed along sections of Interstate 15 and 40 in San Bernardino County. Recent follow-up evaluation for freeway segments where shoulder rumble strips have been in-place for 3 or more years indicated an average reduction of 33 percent statewide.

The Pennsylvania Turnpike tested shoulder rumble strips of various lengths and depths of grooves to select a design with enough sound and vibration to be perceptible in a truck cab and yet not too severe for cars or motorcycles. A before-to-after reduction of 70 percent led to accelerating shoulder rumble strip installation for all roadway segments including those that had been recently repaved and were not scheduled for resurfacing for several more years.

The Turnpike installed shoulder rumble strips on over 53 segments totaling 348 miles of roadway. The resulting crash reduction was 60 percent. Crashes involving single vehicles that drove, rather than slid, off the right side of the roadway were reduced from 3.81 accidents per 100 MVM (2.37/100MVK) before shoulder rumble strip treatment to 1.54/100 MVM (.96/100MVK) after treatment. This type of crash was 11.6 percent of 2,972 total accidents on the Pennsylvania Turnpike in 1990 and 1991 before the shoulder rumble strip installation program could have had any appreciable effect.

Source: Shoulder Rumble Strip Effectiveness: Drift-Off-Road Accident Reductions on the Pennsylvania Turnpike, 1997, TRR 1573.

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How do centerline rumble strips increase highway safety?

Centerline rumble strips are effective at reducing head-on, sideswipe and crossing-the-centerline crashes on two-lane, rural highways. These crashes are of great public concern because they often impact innocent motorists and passengers in a second vehicle. The crash cause is typically driver inattention, error, fatigue, or impairment. An Insurance Institute for Highway Safety study showed all crash types were reduced by 15 percent, while head-on and opposing direction sideswipe crashes involving injuries were reduced by 25 percent.

Crash Reduction Chart
Data compiled by the Insurance Institute for Highway Safety from: “Crash Reduction Following Installation of Centerline Rumble Strips on Rural Two-Lane Roads, IIHS, September 2003

In the year 2000, 20 states had a combined total of 200 miles of centerline rumble strips on a few roadways. The five states with the most miles comprised 100 miles total. By the year 2003, 22 states were using centerline rumble strips for a combined total of approximately 1100 miles. The top five states had 850 miles. Since 2003, at least two states (Pennsylvania and Missouri) have new policies to install centerline rumble strips statewide on their two-lane rural roads.
Kansas State University

Two-Lane, Two-Way Highway Experience

Alaska installed centerline rumble strips in 2000 on horizontal curves on the Seward Highway along Turnagain Arm. Centerline rumble strips were added to Turnagain Hill in 2003 which had a history of head-on collisions. In 2007, two isolated, high crash curves with an increasing history of fatalities over the last five years were also treated on the Sterling Highway (MP 52 and MP 168). Head-on collisions and fatalities have been significantly reduced since these installations. There is not enough data on these short segments to justify drawing conclusions until more years pass. However, data from other states suggests they will be effective at reducing severe crashes in the long term.

Washington reported a 37 percent decrease in crossover collisions and a 55 percent decrease in fatal and disabling crossover collisions over a two year period. This was for 107 miles of rural two lane highway where centerline rumble strips were installed in both passing and no-passing areas.

In Delaware, average yearly head-on collisions decreased by 95 percent after the installation of centerline rumble strips on both passing and no-passing areas on a high crash section of US 301, 3 miles long. Crashes caused by motorists crossing the centerline decreased by 55 percent. Even with a four percent average yearly increase in traffic volumes, there were no fatal accidents reported during the seven-year period after installation of the centerline rumble strips. There were 2 per year in the “before” period (1991-1994)

Nebraska noted a 44 percent reduction in combined fatal and injury crashes following the installation of centerline rumble strips in both passing and no-passing zones.

Missouri conducted a before and after study on a pilot project that implemented centerline rumble strips in 2003. They reported a 60 percent reduction in all crossover centerline crashes and an 84 percent reduction in severe crossover centerline crashes.

Source: Benefit-Cost Evaluation of MoDOT’s Total Striping and Delineation Program, Report # OR09-014, MoDOT, November, 2008.

Minnesota studied 203 miles of roadway, showing every key crash statistic decreased, even those that are typically increase with traffic growth. Total fatal and most severe (Type ‘A’) crashes decreased by 25%. The crash rate and severity rate both decreased by more than 10 percent, even while average annual daily traffic (ADT) increased by nearly 10 percent.

Source: Safety Effects of Centerline Rumble Strips in Minnesota, Report #MN/RC-2008-44, MnDOT

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Why install rumble strips in Alaska?

Fatal and major injury crashes continue to occur each year due to vehicles running off the road or running head-on into opposing traffic. No significant decline in these crashes occurred during the 1990’s, despite the use of rolled-in rumble shoulder rumble strips. As traffic volumes have continued to increase, an increasing number of head-on and run-off-the road crashes caused Alaska to convert to milled-in rumble strips.

In the year 2000, a southcentral Alaska project installed shoulder rumble strips on 375 miles of our main highways. The northern region around Fairbanks installed 500 road miles in 2002. This has been proven to reduce crashes by over 22 percent since installation, and 29 percent in southcentral Alaska. Had Alaska not built rumble strips, data indicates that approximately 25 more fatal and 85 more major injury crashes would have occurred over the five years following installation.

In 2009 and 2010, the Department is scheduled to install shoulder rumble strips on over 150 road miles and along with 100 miles of centerline rumble strips in southcentral Alaska. In the Northern Region, an additional 90 road miles will be treated with shoulder rumble strips in 2009. For southcentral Alaska, the anticipated benefit will be a reduction of an additional 9 fatal crashes and 25 major injury crashes over five years.

State Strategic Highway Safety Plan (SHSP)
Shoulder and centerline rumble strips are identified in the Alaska DOT/PF Strategic Highway Safety Plan (SHSP) as low cost, highly effective strategies in saving lives and injuries. This plan was developed over two years with the input of multiple agencies, and then adopted by Alaska and accepted by the federal government in 2007. The SHSP includes the following:

Shoulder Rumble Strips. Each year, around 40 people die in Alaska each year in run-off-road crashes (on two-lane and four-lane roads). Where shoulder rumble strips are installed, they can eliminate 20 percent or more of these crashes when installed in areas currently without rumble strips. Crash reductions are estimated during snow free months – the benefit when roads are snow covered is anecdotal, but not measured. The SHSP recommends installation and maintenance of rumble strips on all state highways that meet rumble strip installation criteria.

Centerline Rumble Strips. Approximately 15 people die in Alaska each year in head-on crashes, often the innocent victims of errant motorists. Studies show centerline rumble strips could eliminate 12-50 percent of these crashes in locations where installed. This plan recommends installation and maintenance of centerline rumble strips on high-speed rural roads where there is a history of head-on collisions and have also have been identified as a priority for existing and proposed Traffic Safety Corridors.

For information on the SHSP, follow this link.

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What is the effect of shoulder rumble strips on bicyclists?

Drivers drifting off the road not only put their own lives in serious jeopardy, but also the lives of others, including bicyclists riding along the shoulder. An estimated 90% of all cycling fatalities each year are the result of a collision with a car. In Alaska, 11 bicycle crashes have occurred due to errant motorists over 10 years, or about one per year. One half of these resulted in serious injury. Rumble strips can go a long way toward protecting cyclists from drifting drivers.

Even with the safety benefits of rumble strips for cyclists, cycling groups in some states have opposed rumble strips over the concern they are uncomfortable, or possibly dangerous to cyclists who cross them.

Even though shoulder rumble strips have proven safe for cyclists, highway authorities should not ignore protests from cycling advocates who claim the rumble strip is a safety liability. To do so could discourage cyclists from using the very roads that rumble strips have helped make a safe place to ride.

Alaska DOT&PF has developed a rumble strip design that takes rural bicycling into account while still increasing safety for errant motorists:

Gaps are provided for bicycles: Where bicycle travel is allowed, Alaska now uses a 12’ gap and a 68’ rumble on a 80’ cycle. The gap is based on national testing, and the cycle provides an opportunity for a bicyclist traveling at average speed (15 MPH) to cross the rumble strip every 3.1 seconds without contacting the grooves.
Bicycle Illustration
The following clear shoulder width outside of rumble strips are provided for bicyclists:

Segments with guardrail: Provide at least 5’ between the edge of rumble strip and the face of rail (note that this precludes rumble strip installation on 6’ shoulders with guardrail).
No guardrail: Provide at least 4’ between the edge of rumble and the edge of pavement.

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