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| SHARING THE ROAD: VEHICLE SPEED
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Success Stories
• California and Massachusetts recently enacted
laws that give local jurisdictions authority to lower residential
speed limits
from 30 to 25 mph (4). New York allows traffic-calming measures
on local residential streets to lower the average speed to 15 mph.
The nonprofit
organization Transportation Alternatives was instrumental in the
passage of the 1999 New York City Slow Speed and Traffic Calming
Law (5).
• Biking and Walking Solutions, a nonprofit advocacy organization,
started a “Traffic Busters” program in the Merriam Park
neighborhood of Saint Paul. Neighborhood participants pledged to
drive the speed limit, to drive less, and to use alternative means
of transportation more often. Local businesses and the local library
awarded discounts and prizes to program participants. The program
was modeled after the traffic reduction strategies of David Engwicht,
a pioneer in street reclaiming and Safe Routes to Schools in Australia.
While state law sets the speed limits on residential
streets at 30 mph, residents in one Saint Paul neighborhood think 20
mph is better.
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Drivers
traveling at high speeds are less aware of their surroundings and have
less time to notice and react to pedestrians and bicyclists. Relatively
small increases in vehicle speed can greatly increase the chances that a
pedestrian will die in a vehicle-to-pedestrian crash (1). 
Experts on street design say that 20 to 25 mph is the maximum safe speed
for residential streets, but in Minnesota, the law establishes 30 mph
as the speed limit for residential streets. Municipalities can lower
the limit on streets to 25 mph, if signs are posted stating the lower
limit. Signs are expensive to install; even communities that want a lower
speed limit rarely can afford to establish it.
While
30 mph is the maximum speed allowed in an urban or on rural residential
district, most speed limits on collector streets and arterial roads are
set by state departments of transportation, including MnDOT, primarily
using an “85th percentile study.” For an 85th percentile
study, drivers are observed during “free flow” (low-traffic)
conditions. The speed that 85 percent of drivers are traveling under
is considered to be the appropriate speed limit for that road. If most
drivers are going over the posted speed, the limit for the road may be
raised.
The
85 percentile method has been effective at moving vehicles efficiently
on highways, but its effects are not well studied for smaller roads or
roads shared with pedestrians or bicyclists (2). Surrounding land uses
and the presence of large numbers of bicyclists and pedestrians are
not major
factors in determining posted speed limits.
The
Transportation Research Board, a division of the National Academies
of Science, recommends against using 85th percentile studies to set speed
limits on urban arterials “where roadside activities are numerous” and
where “driver misjudgment about appropriate driving speeds poses
high risks to vulnerable road users (eg, pedestrians and bicyclists)” (3).
Enforcement
Most
police officers ticket drivers only when they exceed the speed limit
by 8 to 10 mph, in part because judges tend not to uphold lesser
violations. This means vehicles can be traveling up to 40 mph—the
speed at which 85 percent of pedestrians struck by a car are killed—on
local residential or collector streets where the legal speed is 30.
Recommendations
- Ensure
speed limits maximize safety for all users including drivers, pedestrians
and bicyclists.
- The
Minnesota Legislature should reduce the speed limit for residential
streets from 30 mph to 20 or 25 mph.
- MnDOT
should eliminate the 85th percentile study as the basis for setting
speed limits on non-expressway
urban roads. MnDOT should work with
cities and counties to set speed limits according to the needs and safety
of all users consistent with land uses.
- State
and local governments should increase education and enforcement to
reduce speeding.
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| Footnotes
1 John Pucher and Lewis Djikstra, “Making Walking and Cycling Safer:
Lessons from Europe,” Transportation Quarterly, Vol. 54, No. 3 (summer
2000), 9.
2 Transportation Research Board, Managing Speed: Review Current Practices
for Setting and Enforcing Speed Limits, (Washington, D.C., National Academy
Press: 1998), 2 and John Maczko and Al Shetka, City of Saint Paul, interview
with B. Thoman, 13 May 2002.
3 TRB, Managing Speed, 10.
4 WalkBoston website, accessed from www.walkboston.org/legis.htm on 10
Nov. 2002 and STPP, California Walks, “Pedestrian Safety in California:
Five Years of Progress and Pitfalls,” Aug. 2002, 4, accessed from
www.transact.org.
5 “Pour the Champagne! New Traffic Calming Law Opens Way for Transformation
of City Streets,” Transportation Alternatives Magazine, October/November
1999, accessed on 5 December 2002 from http://www.transalt.org.
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