A Speed Reduction Strategy in Local Street Systems - Institute of ...

principle of the hump design is to force motorists to reduce
speed to a level of about 15 to 20 mph. ‘lEus, if a vehicle
drives over a speed hump at the speed limit of 25 mph for a
residential area, the driver will feel discomfort, yet will not
lose control of the vehicle.
Some speed humps may have a parabolic shape or sometimes
have a flat surface on top. The later type of humps are
COIWOdY used in Austmlia and OCG&OIEd& in the USA.
EXPERIENCE
OF SPEED HUMPS
lleuseofspeed hurnpsas a~ccahningdevice inconsistently
gaining popularity in the USA. Although, Europe and
Australia continue to lead the way in experimenting with and
installing speed humps as a traffic calming device.
The tests conducted in England involved various sizes of speed
humps. After much study, they decided to use 12-feet wide
and 4-inch high humps. They also tested various spacings that
ranged from 160 feet to 510 feet between the humps.
Several cities in the North America repmted use of humps as
trsfilc cahning device. The City of Thousand Oaks, California,
has tested the use of humps extensively. The results of
their before and atler study is as follows
II Site I 85th Percentile Speed II
1. Langtry Drive
2. Clarice Avenue
3. Campbell Drive
4. 130nanza Road
5. AvaIon Road
6. Pyramid Drive
AkhouglL there were other sites where speed humps have been
installe~ these are the locations where there is both before and
afier data available. The after speed data has been verifti by
the authors, by cdecting sample speed data during off-peak
periods using a radar gun in the f~ld.
Table 1 shows the before and after speed and volume data at
the six study sites in Las Vegas, Nevada.
Table 1. Before and after speed and volume data.
Before
Site = ‘
ADT 85# ADT 85#
speed
speed
Langtry Dr. 25 238 29 191 23
CIarice Ave. 25 3,047 38.12 3,316 26
Campbell Dr. 25 4521 - 2,233 27
Bonanza Rd. 25 3,006 34 3,150 27
Avalon Ave. 25 3,455 37.50 2,040 21.86
Pyramid Dr. 25 2,753 29.02 - 23.1
A study in the province of British Columbia, Canat@ reported
benefits accrued from accident reduction in tangible terms in
theuseof various traffic calming devices. Inallcases, the
dollar benefits due to the instaktion of various traffic cahning
devices far outweighed the cost of installation just from the
reduction of accidents.
Such eqeriences have led the authorsof this paper to conduct
a study to test the statisticalsignificanceof speed and traffic
volumereductionin the residentialareasdue to the imtallation
of speed humps. Severalspeed hump sites were selected in
the City of Las Vegas,Nevadato perform this study.
Thebefore speed data for Campbell Drive and after vohnne
data for Pyramid Drive were not available.
The percent changes in speed and trafilc volumes at the six
study sites are as follows
Ii site I Percent Reduction m n
II i 85th % Speed I Am II
Langay Dr. 1 20.6% I 19.7%
STUDYSITES, SPEED AND VOLUME DATA
Rec%ntly the C@ of Las Vegas has been instaMg speed
humps in their residential areas quite aggressively. The
following sites in the City of Las Vegas were selected as a part
of this study
m ,
Avalon Rd. I 41.7% I 40.9% 11
I
20.4% I II
92 Resource Papers for the 1997 International Conference
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