‫ە‬Research Trends and Results

Use of ITS technology toimplement traffic smoothingmeasures at expressway sags

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KANAZAWA Fumihiko, HeadSAKAI Koichi, Senior Researcher
SUZUKI Kazufumi, Researcher
Intelligent Transport System Division, Research Center for Advanced Information Technology
Research Trends and Results(Key words) Sag, traffic congestion, ACC (adaptive cruise control), WUDIILFVLPXODWRU
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1. Introduction
The National Institute for Land and InfrastructureManagement has conducted research to develop avehicle lane utilization rate optimization service basedon the use if ITS SPOT etc. to provide information.
Considering linkages between in-car systems such as
ACC (Adaptive Cruise Control), which controls
distance between vehicles, and services which provide
information from roadside systems, the NILIM is
performing research to develop a service to mitigate
congestion at sags (places where the gradient changes
gently from descending to ascending). In FY2010, it
built a micro-traffic simulator capable of reproducing
the impact on traffic flow of the introduction of these
services on a computer, and trial calculated thecongestion mitigation effectiveness of including
vehicles equipped with the vehicle lane utilization rate
optimization service or ACC in the traffic flow. 
2. Vehicle lane utilization rate optimization service
7KHvehicle lane utilization rate optimization service
provides information to drivers in three stages in order
to correct imbalanced use of passing lanes resulting
from heavy traffic approaching the location ofcongestion. Just in advance of a sag, a “change-lanerequest message” urges drivers to change from thepassing lane to the nearside lane, then near the bottomof the sag, a “keep lane request message” urges driversto stay in the lane they are using, and finally, a“service end message” informs drivers that they areleaving the service section.
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3. Expectations of congestion mitigation at sags byconnecting with vehicle control technology
Recent dazzling progress in vehicle control
technologies has brought ACC and many other suchtechnologies into practical use. This use of ACC,
which has a function which maintains vehicle speed
and the distance between vehicles at constant values,
is counted on to mitigate congestion by restricting
drivers’ unintentional deceleration, which is one causeof congestion at sags.
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4. Construction of a micro-traffic simulator to trial
calculate congestion mitigation effects
Data (traffic volume, cruising speed by vehicle lane
and lane change behavior etc.) obtained from
instruments installed in the past at the Yamato Sag on
the Tomei Expressway (outbound) was used toconstruct a micro-traffic simulator capable ofreproducing traffic flow before and after theoccurrence of congestion at the Yamato Sag(outbound) and before and after the elimination of thiscongestion. When the system was built, in order tothat it could simulate the vehicle lane utilization rate
optimization
service,parametersattwostages—service awareness rate (percentage of drivers
who noticed the information provision) and theacceptability (percentage of the drivers who noticed
the information provision who also responded toit)—were considered. The system could also simulate
vehicle passing behavior, lane changing behavior,
speed reduction characteristic of vehicles in sags, andACC vehicle behavior. 
5. Trial calculation of congestion mitigation
effectiveness
The simulator which was built was used to trial
calculate the congestion mitigation effects of thefollowing services. As a result of these trial
calculations, their usefulness as traffic smoothingmeasures were summarized during FY2010. 1) Congestion mitigation effects of the vehicle lane
utilization rate optimization service2) Congestion mitigation effects of mixing in ACCvehicles3) Congestion mitigation effects of considering thevehicle lane utilization rate optimization service
and mixing in ACC vehicles[Sources]Intelligent Transport System Division web site:
Services to realize AHS/aiming to mitigate congestion
at sags and tunnels
http://www.nilim.go.jp/japanese/its/0frame/under/02ahs/inde
x_02_05.htm