Research Trends and Results

Analysis of the Effects of the Measures for Technical Note of Traffic
Safety Measures and Planning
TAKEMOTO Azuma Researcher
OZAKI Yuta Researcher
YAMAGUCHI Kimihiro Guest Research Engineer
YABU Masayuki HeadRoad Department, Advanced Road Design and Safety Division(Key words) traffic safety measures, analysis of the measure effects, accident black spots, arterial road0%Intersection
improvement
交差点改良(Spacing（コンパクト化）
minimization) at 95
96箇所
locations

20%

40%

61

60%

80%

332

100%
事故減少
ReducedNochange
変化なし

Increased
事故増加

Graph 1 The change of the number of total fatal and injury accidents
after measure implementation (spacing minimization)
3.0
2.52.0変化 1.5率 1.0

Rate of Change

1. Introduction
Ministry of Land, Infrastructure, Transport and Tourism, joined with
National Police Agency, designated as “accident black spots” of thoseintersections and basic road sections which has the high rate and/or
are of frequent occurrence of fatal and injury accident, andPrefectural Public Safety Commission and the responsible roadadministration offices implement cooperated measures. This project
lowers fatal and injury accidents overall at the locations which werecompleted the measures, however, investigated by each location, itfound points to be improved that the measure effects vary and there
increased other types of accidents which were not targeted to reduceby the implementation of the measures, etc. Therefore, theresearchers analyzed the effects of traffic safety measures that wereimplemented up to the present and they clarified consideration points
such as the effects of each construction measure type and its factorsthat cause a dispersion, and effects on traffic behaviors, in order towrite technical notes that will contribute planning and implementationof the more effective safety measures.
2. Analysis of the effects of traffic safety measures
An analysis was conducted of the effects by construction measuretype on 106 construction measure types that were implemented at 10locations for the implemented traffic safety measures on accident
black spots. The rate of change in the number of fatal and injury
accidents before and after measure implementation (= the average
number of the accidents after measure implementation / (divided by)
the average number of the accidents before measureimplementation) showed the result that there were 89 construction
measure types with the rate of change as 1.0 or lower and thenumber of accidents were reduced by the implementation of themeasures in general.
Then, the authors focused on the dispersion of the effects by eachconstruction measure type. The following indicates a couple ofexamples of the analysis results of the spacing minimization
measures of intersection improvements. The purposes of spacing
minimization are: (1) the speed control of left-turn vehicles by “smaller
minimum corner radius” (2) an improvement of visibility forpedestrians through turning traffics by “reallocation of a pedestriancrossing closer to the intersection”, (3) the reduction of dilemma zone
followed by shorter stop line distance by “forwarding the stop linemarking”.
Among 96 locations where implemented spacing minimization,
the rate of change of the number of total fatal and injury accidents
before and after measure implementation resulted that the number ofaccidents was reduced at 61 locations (64%) and was increased at
32 locations (33%)(Graph 1). Next, it was focused on the rate ofchange of the number of fatal and injury accidents by accident type,
among the accidents at pedestrian crossing, at an intersection corner,and on right-turn traffic which was targeted to reduce by spacing
minimization, both the median and the average of the rate of change

0.5Median
中央値
ave+ SD
平均+標準偏差ave
平均ave- SD
平均‐標準偏差0.0

PD横断歩道crossing at出会い頭intersection 左折時
L-turnRE
colR-turn
追突
右折時
横断中
* The rateof change = theaverage number of the accidents after measure※変化率＝対策後の平均事故件数／対策前の平均事故件数
implementation / the average number of the accidents before measure implementation

Graph 2 The rate of change of fatal and injury accidents by accident
type (spacing minimization)
were less than 1.0 and that there were many locations that werereduced the number of accidents (Graph 2). On the other hand, themedian of the rate of change was less than 1.0 on rear-end collisions
and at right turn and the number of accidents were reduced at half ormore locations, however, the average was larger than 1.0 and there
were locations that increased the number of accidents.
To recognize the factors of increased accidents, the researchersinvestigated the effects on traffic behaviors by implementation of themeasures. It was found that there was following vehicle’s sudden
breaking after rapid deceleration of the left-turn vehicle at locations
that implemented “smaller minimum corner radius”. It may beconsidered effective to implement a speed control measure forleft-turn vehicles before the intersection and/or other measures asmultiple measures for the applicable locations.
3. Summary and the points to improve
From the above results, it was confirmed that it was shown
effective for the accident types that were targeted to reduce by theimplementations of the measures while it is possible to increase thenumber of accidents among other accident types depending on thelocation. In order to implement traffic safety measure more effectively,
it is important to select the construction measure type with thoroughestimation of traffic condition changes after measure, and it isnecessary to make investigations suitable for the site location such as
implementing multiple measures based on the necessity.
In the future, it will be further summarized the results of theanalysis of the effects on traffic safety measures, consideration points
at measure implementation, etc. by accident type and by construction
measure type, and is planned to write technical notes which will
support planning and implementation of the more effective traffic
safety measures.