٨Research Trends and Results

A method of using rubberpoles to control speed onresidential roads

KANEKO Masahiro, Head ITO Katsuhiro, Guest Researcher
HONDA Hajime, Senior Researcher
Advanced Road Design and Safety Division, Road Department

Research Trends and Results(Key words) Residential road, speed control, rubber poles, chicane, narrowing 
1. Introduction
As a traffic safety measure for residential roads,
speed control measures have been taken using humps,
narrowings, or other structures which control thetraveling speed of automobiles (below called,“devices”). But, many humps or narrowings executedin the past are expensive, because they often requireroad reconstruction. So while many people are calling
for traffic safety measures on nearby residential roads,
with the finances of local governments restricted, theywish to implement simpler measures at many locations,even though these may be somewhat less effective.
This research included a survey to clarify the degreeof speed control effectiveness of constructing chicanes
or narrowings using simple devices (rubber poles) on
actual roads and a study of effective and simple speedcontrol measures.
2. Implementing a social experiment using rubberpolesIn 2009, at the locations of 15 narrowings, 10chicanes, and 5 slaloms, the relationships of theirshapes with the speeds of automobiles travelingthrough them were surveyed and analyzed. The results
show that in order to lower the 85th percentile speed
to below 30km/h, the slowing effects of the chicane isgreater than that of the narrowing, and that regarding
the shape of the chicane, the relationship F/W҇0.37
should be established between vehicle lane width W
and fault width F.
L0:
Chicane length㪣㪇䋺䉲䉬䉟䊮ᑧ㐳

F:Fault width㪝䋺䊐䉤䊦䊃᏷O:
lateral displacement㪦䋺ᮮᣇะ䈱䈝䉏

D:vehicle lane width㪛䋺ゞ㆏᏷ຬ
W: total width㪮䋺✚᏷ຬBut, the chicane is LO (chicane length) = L1 (curve length) + L2 (Fault length)

Figure: Example of the Shape of a Chicane (Slalom)
And in 2010, in cooperation with Kumagaya City in
Saitama Prefecture, the division used rubber poles to
Photo View of the Social Experiment (Chicane)construct a chicane (fault width of about 2m) which
maintained the above F/W҇0.37 relationship on aone-way street with vehicle lane width of about 5.5m,
and performed a social experiment with a total of threepatterns of chicanes and narrowings with varying
intervals and measured automobile traveling speed toclarify whether or not speed reduction effects wereobtained and to undertake simple measures while
maintaining this effectiveness.
The 85th percentile speed which was about 39km/h
without the rubber poles, fell to about 35km/h in two
patterns with chicane interval of 35m and 50m, which
was speed reduction effects of about 4km/h. At thesame time, about half of the automobiles traveled atspeeds of 30km/h or less in a section of about 100m or
more in an observation section of 180m.
At narrowings at 50m intervals, the 85th percentile
speed fell only slightly, by about 2km/h toapproximately 36km/h, with benefits obtained by all
patterns. And among these, as imagined, the chicanes
were more effective, and in the chicane cases, somepedestrians complained that they feel they are
dangerous, revealing that it is necessary to separately
study ways to improve the feeling of security theyprovide.
3. Future developments
We are considering summarizing the results of thissocial experiment and precautions concerning theinstallation of existing devices (installation interval,distance required from frontage, etc.) as a technicaldocument, and to give support enabling local
governments to introduce speed control measures alittle more easily.