٨Research Trends and Results

Method of making an early
verification of the effectiveness of atraffic accident measure using video
image data etc.


OZAKI Yuta, Researcher
HASHIMOTO Hiroki, Guest Researcher
KANEKO Masahiro, Head
Advanced Road Design and Safety Division
1. IntroductionTraffic safety measure projects should be
implemented based on the PDCA cycle, which
includes the steps—analyze causes of accidents, study
countermeasures, implement them, evaluate theireffectiveness, and study and implement supplementary
countermeasures—in order to carry out more effectivecountermeasures. And in order to quickly discover
their effectiveness, this PDCA cycle must be
implemented as efficiently as possible. And theeffectiveness evaluation step in the PDCA cycle has
been done by collecting accident data before and after
the countermeasure. But to perform an accurate
evaluation based on accidents, it is necessary to collectdata representing several years, so it takes a long time
to make a reliable evaluation.
So the NILIM has developed a method ofevaluating the effectiveness of a countermeasure basedon speed data obtained from video images etc. andconflict behavior of automobiles to supplement
methods of evaluating effectiveness based on accident
data.

2. Effectiveness evaluations by analyzing vehicle
behavior images
Figure 1 shows the distributions of speeds ofautomobiles passing the experiment locations before
and after taking temporary countermeasures. The
speed is interpreted from video images. The temporary
countermeasures taken for this experiment were laying
a simple Mat with a level difference on the road inorder to alert drivers to the road ahead and slow themdown, and at the same time, installing
attention-getting signs to warn drivers to control their
speed and alert them to the danger of rear-end
collisions if they change lanes.
It is confirmed that the temporary countermeasures
reduced speed. Although it will be necessary tocontinue to verify the relationship between speed andaccidents, it is possible to evaluate the degree ofachievement of the targets of the countermeasures (for100%

Cumulative frequency(%)

Research Trends and Results(Key words) Conflict phenomenon, video image, traffic accident measure effectiveness 80%
60%
40%

Averagespeed before measure:ኻ╷೨ᐔဋㅦᐲ䋺㪌㪊㪅㪏㫂㫄㪆㪿
53.8km/hኻ╷ᓟᐔဋㅦᐲ䋺㪋㪐㪅㪈㫂㫄㪆㪿
Average speed after measure: 49.1km/h㸢㪋㪅㪎㫂㫄㪆㪿ૐਅ
p4.7km/h
reduction

Beforethe measureኻ╷೨Afterthe measureኻ╷ᓟ
Dotted line is cumulate rate̪᛬✢䈲⚥ⓍᲧ₸20%0%
䌾20 䌾25 䌾30䌾35 䌾40䌾45 䌾50 䌾55䌾60 䌾65 䌾70䌾75 䌾80 䋨km/h䋩

Figure 1. Change of Driving Speed Distribution AfterCountermeasure
Table 1. Change of Conflict Phenomena
Occurrence Frequency After Measure
Conflict phenomenon pattern

Occurrence frequency (times/24 hours)
Before measure
After measureAbruptly changes lanes
Rapidly nears leading vehicle
Total

21122

101

this experiment, reducing speed) based on thecountermeasure work methods which we selected (forthe experiment, simple Mat, etc.).
Table 1 organizes changes of the frequency ofconflict phenomena. It treats dangerous phenomena
accompanying avoidance actions such as emergency
braking or emergency steering as conflict phenomena.
The frequency of conflict phenomena is totaled by thesame survey personnel visually confirming video
images both before and after temporary measures aretaken.
It revealed that conflict phenomena fell sharply
after the measure. But with the correlation of accidents
with conflict phenomena not fully confirmed, in order
to apply this method to verify the effectiveness ofcountermeasures, it is still necessary to analyze theaccident – conflict phenomena correlation. At theexperiment locations, 17 rear-end collisions occurred
during the four years that was the criterion foraccident data collection periods. If correlation withaccident data is confirmed, it will be possible toperform evaluations using the same quantity of data asaccident data based on 24 hour video image data.
3. Summing up and future challenges
As explained above, by interpreting speed and other
aspects of vehicle behavior based on image dataobtained before and after countermeasures, it will bepossible to confirm whether or not the selected
countermeasure works are fully effective. And byorganizing the correlation of accidents and conflictphenomena it will be possible to quickly evaluate theeffectiveness of traffic safety measures.  ٨Research Trends and Results