●Research Trends and Results

Research on early verification method for traffic safety
countermeasure effectiveness based on traffic behavior
observations
OZAKI Yuta, Researcher
YAMAGUCHI Kimihiro, Guest Researcher Engineer
TAKAMIYA Susumu(PhD. (Arts and Sciences)), Head,Road Department, Advanced Road Design and Safety Division(Key Words) Traffic behavior, early verification of countermeasure effectiveness2. Verification of traffic safety countermeasureeffectiveness by observing traffic behavior
This research was a trial verification ofcountermeasure effectiveness based on a number ofindices. The following is an example.
The object location is a location where thenumber of right turn collisions was reduced by theright turn guide line. The right turn guide line which
was installed guides cars whose drivers intend to turnright to the appropriate position to stop and wait
before turning right at the intersection. Its purpose is
to make it easy for these drivers to confirm thelocations of cars traveling straight from the opposite
direction (oncoming cars), so they do not start theirturn at a dangerous time.
First, as an index to quantitatively represent changeof traffic behavior (time to start the right turn) to be
improved by the right turn guide line, the position of
oncoming cars at the time the right turn begins (timewhen the car turning right passes the waiting location
indicated by a white line on top of the right turn guideline) was measured. The location of the oncoming car
is represented by the distance to the stop line from the
car among oncoming cars which is nearest to the stopline. Figure 1 organizes the correlation between thefrequency that the oncoming car location at the time aright turn starts was at or below the thresholds (30m,40, 60m) with the average annual number of right turncollisions. The number of cars turning right during the530mor less30m以下

Difference between times the two cars enter
the collision area (times/90min.)
衝突エリアへの進入時間差（回/90分）

Oncoming car traveling location at start of right6
turn by the turning car (times/90min.)
右折開始時の対向直進車位置（回/90分）

1. Introduction
Traffic safety countermeasure effectiveness isverified mainly using accident data. However, theoccurrence probability of traffic accidents is low so ittakes about four years to collect the accident datanecessary for verification of effectiveness, and there
are cases where, if a follow-up countermeasure isneeded, the confirmation of its need and its
implementation are delayed.
So the National Institute for Land and InfrastructureManagement aims to establish a method of rapidly
verifying the effectiveness of countermeasures byobserving change of traffic behavior after theimplementation of each countermeasure.

40mor less
40m以下

560m
or less
60m以下

43
2
100

12

右直事故件数（件/年）
Numberof right turn collisions(accidents/year)

Figure 1. Locations ofOncoming Cars at Start ofRight Turn

35s or less
5s以下
4s or less
4s以下

43s or less
3s以下

3

2

100

12

右直事故件数（件/年）
Numberof right turn collisions(accidents/year)

Figure 2. Difference inTime of Entry toCollision Are

time period of the measurements was 18 before thecountermeasure and was almost identical at 17 after
the countermeasure. A positive correlation was seen
between change of the number of accidents andchange of the index, and it is assumed that it ispossible to measure the reduction of accidents basedon the reduction of the frequency the location of theoncoming car when a driver started a right turn was at
or lower than the threshold value.
It is considered to be possible to verify theeffectiveness of a countermeasure based on an index
which represents the change of traffic behavior to beimproved by the countermeasure in this way.
Next, as an index which quantitatively represents
the danger of a collision, the area where the travelingcourses of a car turning right and an oncoming car
overlap was defined as the collision area, and thedifference between the times the cars enter this area
was measured. Figure 2 organizes the correlation of
the frequency that the difference in entry time is at orbelow the threshold (3 seconds, 4 seconds, 5 seconds)
with the annual number of right turn car – oncoming
car accidents. There is a positive correlation with thenumber of accidents, so it can be hypothesized thataccidents are reduced by lowering the frequency thatthe difference between the times of entry to the3

●Research Trends and Results
collision area is at or lower than the threshold value.
It is assumed to be possible to verify
countermeasure effectiveness, even with an index
representing the danger of collision in this way.
3. Summing up and future challenges
The above results show that in order to verify theeffectiveness of a countermeasure based on traffic
behavior, selecting the index is important. In the future,
it will be clarified what kinds of traffic behavior
indices should be used for which kinds of accidents
and traffic safety countermeasures, to establish early
verification methods for countermeasure effectivenessbased on traffic behavior.