Boosting Roadway Safety with Rumble Strips
Approximately one-third of all traffic fatalities and serious injuries
in the United States annually are due to run-off-road crashes. In 2000,
almost 16,000 deaths were attributed to these types of accidents. Such
statistics have caused the transportation community in recent years
to take steps aimed at keeping motorists on the road, rather than relying
on clear roadsides and traffic barriers to minimize crash severities.
One answer: rumble strips. Richard Powers of the Federal Highway Administration's
(FHWA) Office of Safety Design says, "Our primary goal is to reduce
single-vehicle crashes and fatalities, and rumble strips have proven
to be a cost-effective way to keep motorists on the roadway."
Rumble strips are raised or grooved patterns constructed primarily
along paved shoulders. When vehicle tires pass over the strips, they
produce a sudden rumbling and vibration in the car. Both the sound and
the vibration alert fatigued or distracted drivers that they are beginning
to drift off the road.
FHWA is spearheading a movement to increase nationwide use of rumble
strips. A new technical advisory released by FHWA in December 2001,
Roadway Shoulder Rumble Strips, contained the latest information
on the state-of-the-practice design and installation of rumble strips,
including recommendations for minimizing the adverse effects rumble
strips may have on bicyclists using roadway shoulders. The advisory,
which also includes an extensive list of reference materials on rumble
strip use and effectiveness, is posted on the Web at www.fhwa.dot.gov/legsregs/directives/techadvs/t504035.htm.
Numerous States have performed studies on the effectiveness of rumble
strips, with the resulting statistics revealing dramatic success rates.
In 1985, the California Department of Transportation (DOT) performed
a before-and-after study where it installed rumble strips along sections
of Interstates 15 and 40 in San Bernardino County. The study revealed
a 49 percent decrease in the number of run-off-road crashes in the areas
with rumble strips. Recent follow-up evaluations of freeway segments
where shoulder rumble strips have been in place for 3 or more years
have shown a 33 percent average reduction in run-off-road accidents.
In the early 1990s, Pennsylvania performed an extensive review of the
effectiveness of shoulder rumble strips. As part of this project, the
Pennsylvania Turnpike developed a shoulder rumble strip that it called
the Sonic Nap Alert Pattern (SNAP). Following the installation of SNAP,
the monthly number of run-off-road accidents decreased by 70 percent.
A report on the project can be viewed on the Web at http://safety.fhwa.dot.gov/roadway_dept/rumble/synthesis/pro_res_rumble_library.htm#Papers.
The Delaware DOT's US Route 301 Centerline Rumble Strip Project provides
some of the most compelling evidence concerning the success of rumble
strips. After experiencing a high fatality rate from head-on collisions
on Route 301, the Delaware DOT installed centerline rumble strips along
the roadway. The result was a 90 percent decrease in the head-on collision
rate and a zero fatality rate. These improvements were achieved despite
a 30 percent increase in traffic. The project was awarded one of the
2001 National Highway Safety Awards by FHWA.
In addition to increased safety, rumble strips have been shown to cut
costs. Several States have analyzed the benefit/cost ratio of shoulder
strips, and the results are as dramatic as the accident reduction rates.
New York State Thruway data indicates a benefit/cost ratio ranging from
66:1 to a high of 182:1. The Nevada DOT found that with a benefit/cost
ratio ranging from 30:1 to more than 60:1, rumble strips are more cost-effective
than many other safety features, including guardrails, culvert-end treatments,
and slope flattening. And a Maine DOT survey of 50 State DOTs identified
a benefit/cost ratio of 50:1 for milled rumble strips on rural Interstates
nationwide.
Looking at the future, to build on current rumble strip successes,
additional installations and evaluations of centerline rumble strips
and shoulder rumble strips on two-lane rural roads are needed.
For more information on using rumble strips, contact Richard Powers
of FHWA at 202-366-1320 (email: richard.powers@fhwa.dot.gov)
or visit FHWA's Rumble Strips Web site at http://safety.fhwa.dot.gov/roadway_dept/rumble/.
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Articles in this issue:
Prefabricated Bridge Elements and Systems: A Winning
Idea
Boosting Roadway Safety with Rumble Strips
Preserving the Future of Pennsylvania Bridges
Work Zone Research from A to Z
Design Guide Offers New Look at Mitigating Highway
Rockfall Hazards
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