Shoko Oikawa

Features of fatal pedestrian injuries in vehicle-to-pedestrian accidents in Japan

The number of traffic deaths in Japan was 4,612 in 2011. Looking at the road accident fatalities, it revealed that pedestrians accounted for the highest number in 2011 (1,686, 36.6%). To develop safety countermeasures to decrease the severity of injuries and to reduce the number of deaths in traffic accidents, the detailed characteristics of pedestrian injury in vehicle-to-pedestrian crashes are necessary. The purpose of this study is to understand the scenarios of vehicle accidents in which pedestrians suffer fatal injuries. In the present study, we investigated the characteristics of pedestrian injuries in fatal crashes from accident analyses and compared them to head injury severity levels in impact tests against a road pavement and vehicle contact surfaces. In the accident analyses, we investigated the main body regions injured, that is, the most serious extent of injuries over the whole body of pedestrians by using macro vehicle-pedestrian accident data from database of the Institute for Traffic Accident Research and Data Analysis (ITARDA) of Japan. In comparing the differences in injury frequencies for various body regions between 1999 and 2009, it is noted that the frequencies of pedestrian fatalities due to head injuries were significantly reduced. The result indicated that even though head injuries were the most frequent cause of pedestrian fatalities in traffic accidents, the introduction of pedestrian head protection regulation in Japan in 2005 could be considered effective in reducing fatal head injuries. On the other hand, the frequencies of pedestrian fatalities due to hip injuries increased significantly in sedans, light passenger cars, and light cargo vans. Using the macro accident data in 2009, we investigated the frequency of pedestrian fatalities by gender, age group, vehicle travel speed, and fatal head injuries due to vehicle impacts or road pavement impacts. The results also indicated that the frequencies of female pedestrian fatalities due to hip injuries were significantly higher than those of males. Additionally, the results showed that the frequency of pedestrian fatalities due to hip injuries for the age group of over 65 years was significantly higher than that of the industrial age group (aged 13-59). Focusing on the frequency of pedestrian fatalities due to hip injuries in all age groups, vehicle travel speed appeared likely not to be an extremely important factor in increasing fatal hip injuries. In examining the differences in the frequency of fatal head injuries due to contacts with vehicles or road pavements, it is noted that injury frequency in crashes involving vehicles travelling at high speeds were significantly higher than those at lower speeds for pedestrians over 60 years of age. Focusing on head injury severity levels in impact tests against a road and vehicle surfaces using an adult pedestrian headform impactor, the impacts against a road pavement (HIC 6525) was considered to be more severe than those against vehicle front components with high stiffness (HIC from 2600 to 4032). Language: en

Temporal and fine-grained pedestrian action recognition on driving recorder database

The paper presents an emerging issue of fine-grained pedestrian action recognition that induces an advanced pre-crush safety to estimate a pedestrian intention in advance. The fine-grained pedestrian actions include visually slight differences (e.g., walking straight and crossing), which are difficult to distinguish from each other. It is believed that the fine-grained action recognition induces a pedestrian intention estimation for a helpful advanced driver-assistance systems (ADAS). The following difficulties have been studied to achieve a fine-grained and accurate pedestrian action recognition: (i) In order to analyze the fine-grained motion of a pedestrian appearance in the vehicle-mounted drive recorder, a method to describe subtle change of motion characteristics occurring in a short time is necessary; (ii) even when the background moves greatly due to the driving of the vehicle, it is necessary to detect changes in subtle motion of the pedestrian; (iii) the collection of large-scale fine-grained actions is very difficult, and therefore a relatively small database should be focused. We find out how to learn an effective recognition model with only a small-scale database. Here, we have thoroughly evaluated several types of configurations to explore an effective approach in fine-grained pedestrian action recognition without a large-scale database. Moreover, two different datasets have been collected in order to raise the issue. Finally, our proposal attained 91.01% on National Traffic Science and Environment Laboratory database (NTSEL) and 53.23% on the near-miss driving recorder database (NDRDB). The paper has improved +8.28% and +6.53% from baseline two-stream fusion convnets.

Analysis of car-to-bicycle approach patterns for developing active safety devices

ABSTRACT Objective: To reduce the severity of injuries and the number of cyclist deaths in traffic accidents, active safety devices providing cyclist detection are considered to be effective countermeasures. The features of car-to-bicycle collisions need to be known in detail to develop such safety devices. Methods: The study investigated near-miss situations captured by drive recorders installed in passenger cars. Because similarities in the approach patterns between near-miss incidents and real-world fatal cyclist accidents in Japan were confirmed, we analyzed the 229 near-miss incident data via video capturing bicycles crossing the road in front of forward-moving cars. Using a video frame captured by a drive recorder, the time to collision (TTC) was calculated from the cars velocity and the distance between the car and bicycle at the moment when the bicycle initially appeared. Results: The average TTC in the cases where bicycles emerged from behind obstructions was shorter than that in the cases where drivers had unobstructed views of the bicycles. In comparing the TTC of car-to-bicycle near-miss incidents to the previously obtained results of car-to-pedestrian near-miss incidents, it was determined that the average TTC in car-to-bicycle near-miss incidents was significantly longer than that in car-to-pedestrian near-miss incidents. Conclusions: When considering the TTC in the test protocol of evaluation for safety performance of active safety devices, we propose individual TTCs for evaluation of cyclist and pedestrian detections, respectively. In the test protocols, the following 2 scenarios should be employed: bicycle emerging from behind an unobstructed view and bicycle emerging from behind obstructions.

Features of serious pedestrian injuries in vehicle-to-pedestrian accidents in Japan

ABSTRACT This study clarifies vehicle accident scenarios in which pedestrians suffer serious injuries. We investigated the characteristics of serious pedestrian injuries in accidents, using vehicle-to-pedestrian accident data for 1999 and 2009 in Japan. We focused on the main body region of seriously injured pedestrians considering different factors including the accident year, vehicle type, travel speed, and pedestrian gender and age. The results indicate that sedans, mini vans and light passenger cars tended to injure pedestrians’ legs more frequently, while box vans and light cargo vans tended to injure the head more frequently. The results also show that female pedestrians suffered hip injuries more often than male pedestrians in accidents involving sedans, mini vans, light passenger cars and light cargo vans. In accidents involving sedans, it was revealed that the head and hip were injured statistically more frequently at high vehicle travel speed than at low vehicle travel speed in all age groups.

Factors causing abdominal injuries to a vehicle occupant in frontal impact accidents

ABSTRACT Vehicle occupants were killed in 33% of all fatal traffic accidents in Japan in 2014. The abdomen is associated with the highest risks of serious injuries and fatalities, so we have investigated the causes of abdominal injuries to vehicle occupants. Fifty-four percent of vehicles struck in vehicle-versus-vehicle accidents were impacted from the front. An investigation on accident details determined that lap belts caused serious abdominal injuries. Residual deformation marks suggest that seats move vertically during a frontal impact. The purpose of this study was to clarify the effect of vertical movements of the seat on the lap belt in the event of a frontal impact. We investigated the phenomenon using simulations and an anthropomorphic 50th percentile male Hybrid III dummy model wearing a three-point seat belt. Our results revealed that the lap belt slipped from its initial position around the dummy waist when the seat height was lowered by 150 mm. We concluded that abdominal injuries could be caused by vertical movements in the seat during vehicle-versus-vehicle frontal impacts.

Effectiveness of wearing a bicycle helmet for impacts against the front of a vehicle and the road surface

Abstract Objective: To assess the effect of wearing a bicycle helmet using an adult headform in terms of the head injury criterion (HIC) when the frontal and lateral parts of the helmet impact a vehicle body and also when the frontal part of the helmet impacts the road surface. Methods: The adult headform was made to impact the hood, windscreen, roof top, and roof side rail of a vehicle body at an impact velocity of 35 km/h, which is a common head-to-vehicle impact velocity in real-world cyclist–vehicle collisions, in which the vehicle impacts the cyclist at 40 km/h. For the road surface impact experiments, we set a drop height of 1.5 m (impact velocity of 20 km/h). Results: Helmet usage helped to reduce the HIC when the frontal and lateral parts of the helmet impacted vehicle parts other than the hood. The HIC reduction for the frontal impact was greater than that for the lateral impact. Moreover, the higher the stiffness index of the vehicle structure, the greater was the HIC reduction. However, helmet usage was ineffective for reducing skull fracture risk (HIC 2558) when the lateral part of the helmet impacted stiffer parts of the vehicle, such as the roof side rail close to the B-pillar. Helmet usage helped to reduce the HIC by 91% when the frontal part of the helmet impacted the road surface. Conclusions: Wearing a helmet reduces skull fracture risk when the frontal and lateral parts of the helmet impact vehicle parts (excluding the hood) at 35 km/h and the road surface at 20 km/h. However, when the lateral part of the helmet impacts the B-pillar, the helmet cannot effectively reduce the skull fracture risk at these real-world velocities.

Features of fatal injuries in older cyclists in vehicle–bicycle accidents in Japan

ABSTRACT Objective: The purpose of this study was to identify and better understand the features of fatal injuries in cyclists aged 75 years and over involved in collisions with either hood- or van-type vehicles. Methods: This study investigated the fatal injuries of cyclists aged 75 years old and over by analyzing accident data. We focused on the body regions to which the fatal injury occurred using vehicle–bicycle accident data from the Institute for Traffic Accident Research and Data Analysis (ITARDA) in Japan. Using data from 2009 to 2013, we examined the frequency of fatally injured body region by gender, age, and actual vehicle travel speed. We investigated any significant differences in distributions of fatal injuries by body region for cyclists aged 75 years and over using chi-square tests to compare with cyclists in other age groups. We also investigated the cause of fatal head injuries, such as impact with a road surface or vehicle. Results: The results indicated that head injuries were the most common cause of fatalities among the study group. At low vehicle travel speeds for both hood- and van-type vehicles, fatalities were most likely to be the result of head impacts against the road surface. The percentage of fatalities following hip injuries was significantly higher for cyclists aged 75 years and over than for those aged 65–74 or 13–59 in impacts with hood-type vehicles. It was also higher for women than men in the over-75 age group in impacts with these vehicles. Conclusions: For cyclists aged 75 years and over, wearing a helmet may be helpful to prevent head injuries in vehicle-to-cyclist accidents. It may also be helpful to introduce some safety measures to prevent hip injuries, given the higher level of fatalities following hip injury among all cyclists aged 75 and over, particularly women.

Characteristics of the gaze of a driver following a preceding vehicle and cognition time for an approaching vehicle

ABSTRACT The effect of eye movement on the gaze area was investigated using a driving simulator when a driver simply followed a preceding vehicle on a straight road under two conditions; while focusing on a vehicle and while focusing on a vehicle and red points in a wide area of the front screen. The area of the distribution of the gaze points was greater in the latter case, especially on the right-hand side. The results suggest that a tool that forces a driver to gaze across a wide area would encourage gazing in side areas. The study also investigated the cognition time of a driver as other vehicles suddenly emerged at intersections. The cognition time at the first intersection was significantly longer than that at the last intersection, suggesting that the first event of an approaching car enlarged the area of the drivers vision as the driver displayed greater caution.