Pedestrian-vehicle Conflict Research Articles

VEHICLE – PEDESTRIAN CONFLICT: A CASE STUDY IN UNIVERSITI PUTRA MALAYSIA

Vehicle-pedestrian conflict is a commonly unsafe event that occurs in both urban and rural areas, especially in developing countries. It is still an open research topic, mostly in traffic safety and urban planning, which is utilised for evaluating the behaviours of vehicles and pedestrians at a non-signalised marked walkway. Three stations were selected based on higher daily activities to calculate the regularity of pedestrian movement. A manual calculation method was applied, and the calculation was done only during the daytime. Three different teams were formed to obtain the measurements at the three different sampling points simultaneously. A present study on preliminary vehicle-pedestrian conflict reveals the frequency of pedestrians in a concentrated area and its Level of Service (LOS) in Universiti Putra Malaysia (UPM) Serdang. The findings show that rush hour occurs during the mid-day in weekday, when students have finished their classes and adults have gone out for other businesses.

Assessing right-turning vehicle-pedestrian conflicts at intersections using an integrated microscopic simulation model

Frequent vehicle-pedestrian conflicts deserve special attention for safety assessment at intersections. This study helps verify how the simulation as an innovative approach can be utilized for right-turning vehicle-pedestrian conflict assessment at intersection crosswalks prior to implementation. Various behavior models such as vehicle turning path, turning speed, gap acceptance model and pedestrian behavior model, have been established. Through integrating the calibrated models into one simulation platform, the stochastic behavior of vehicles and pedestrians under different geometric layouts and operational conditions can be reproduced. Based on the field data collected by an unmanned aerial vehicle (UAV) at two urban intersections in Beijing, China, it was demonstrated through validation of surrogate safety measures (SSMs), i.e., Post Encroachment Time (PET) and vehicle passing speed at conflict points, that the simulation model can reasonably represent the frequency and severity of conflict occurrence at signalized crosswalks. The sensitivity analysis results indicated that large dimensions and turning angles of intersections tend to result in undesirable safety performance.

Looking for an optimal pedal layout to improve the driving performance of patients with diabetic peripheral neuropathy

Diabetes can undermine people's ability to drive safely, but most previous studies have focused on its deterioration of the central nervous system. This study sought to investigate how diabetic peripheral neuropathy (DPN), a common complication of diabetes characterized by reduced sensitivity of the limbs, can influence people's braking behavior and other safety-related measures of driving. In addition, it also tested how such a deteriorating effect can be reduced by using certain pedal layout designs.In total, 29 healthy drivers and 31 drivers of type 2 diabetes matched in demographic variables were invited to participate in this study. The participants with type 2 diabetes (they are from here on out referred to as “patients")were then split into two subgroups based on the severity of DPN using the median of the Semmes–Weinstein monofilaments Examination (SWME) scores. All three groups of participants finished a series of vehicle-pedestrian conflict tasks in a driving simulator using nine different types of pedal layouts. These layouts varied in the lateral distance between the accelerator and the brake (45 mm, 60 mm, and 75 mm) and the width of brake pedals (50 mm, 70 mm, 90 mm). The results showed that patients with serious DPN had longer brake reaction times (BRT) and shorter minimum distance-to-collision (DTC) as compared to the other two groups. However, the effects of such a disadvantage varied across different pedal layouts. When the accelerator-brake distance was 45 mm, patients with serious DPN showed no compromised driving performance as compared to other two groups.In conclusion, we found the DPN could undermine driving performance of participants with type 2 diabetes, and a closer accelerator-brake lateral distance (45 mm) may be an optimal choice for them to counteract such a negative influence.

Benefits of Redundant Visual In-Vehicle Information in Pedestrian–Vehicle Conflict Scenarios

The paper provides information relevant to the development of driver and pedestrian safety systems by examining drivers’ responses to infrastructure-based safety messages (DII) with a redundant in-vehicle display component. A driving simulator was used to create a conflict situation which required an immediate driver response to avoid a collision. At the start of the event, a pedestrian was occluded by a truck at an intersection. Partway through the event, the pedestrian dashed into the road and into the driver’s path. When redundant visual in-vehicle alerting messages were provided, drivers released the throttle more quickly, engaged the brake more quickly, and had longer minimum time to collision relative to the baseline condition which lacked visual alerts. This was an improvement over the DII-only condition, where drivers did not brake more quickly relative to baseline and had only marginally longer minimum time to collision compared with the baseline condition. The findings suggest that redundant in-vehicle message information provides a benefit to many drivers over systems that use only infrastructure-based safety systems in vehicle–pedestrian conflicts.

Optimizing Mixed Pedestrian-Vehicle Evacuation via Adaptive Network Reconfiguration

Insufficient network capacity and conflicts between pedestrians and vehicles at roadway intersections can be critical obstacles to the operational efficiency of evacuation activities. Reducing pedestrian—vehicle conflict points and expanding network capacities are two possible approaches to improving operational efficiency, especially when network accessibility varies in different evacuation stages. This paper integrates two types of network reconfiguration strategies, namely, the use of contraflow lane reversal for road lanes and pedestrian walkways and time-dependent conflict point elimination by separating pedestrian and vehicle flows with physical barriers at road intersections, to strategize pedestrian and vehicle moving directions during a mass evacuation. A multiobjective optimization model is formulated to adaptively select the appropriate locations for barriers according to different evacuation phases, and the model is solved by a modified genetic algorithm-based heuristic approach. An experiment on optimizing an urban regional evacuation network configuration in the case of a toxic gas leak accident was carried out to validate the proposed model. The numerical results show an increase of approximately 15% in the maximum evacuee throughput and a reduction of approximately 65% in the average exposure risk of evacuees of the optimal plans compared with the uncontrolled plan.

Automatic Vehicle-Pedestrian Conflict Identification With Trajectories of Road Users Extracted From Roadside LiDAR Sensors Using a Rule-Based Method

Vehicle-pedestrian conflicts have been the major concern for traffic safety. Surrogate safety measures are widely applied for pedestrian safety evaluation. However, how to quickly identify the vehicle-pedestrian surrogate safety measures at the individual site is challenging due to the difficulty of obtaining the high-resolution trajectories of road users. This paper presented an effective method to generate the high-resolution traffic trajectories from the roadside deployed Light Detection and Ranging (LiDAR) sensor. The vehicle-pedestrian conflicts can then be identified from the trajectories simply using the speed-distance profile (SDP) of the vehicles. The SDP can be used to develop a rule-based method for vehicle-pedestrian identification. The events can be divided into different risk levels based on the spatial distribution of the SDP. The case study shows that the rule-based method can detect vehicle-pedestrian near-crash events effectively. The other indicators, such as widely used time-to-collision (TTC) or deceleration rate to avoid a crash (DRAC), can be also obtained from the SDP. The engineers can also adjust the thresholds in the rule-based method to meet the specific requirements at different sites. The proposed method can be extended to identify vehicle-vehicle conflicts or vehicle-bicycle conflicts in future studies.

Drivers’ effective decelerating zone in an urban Vehicle-Pedestrian conflict situation: Observational studies and analyses

To analyse the drivers’ decelerating behavior in conflict avoidance process under Vehicle-Pedestrian conflict situation is accordingly a surrogate method for the guidance of driver evasive manoeuvre and improving the active driving safety. Field observation data has been collected by video recording and image processing at urban unsignalized midblock crosswalks in Beijng, China and Munich, Germany. The relationship between deceleration rate and vehicle speed has been statistically described. By analyzing how the time-related measures (Vehicle Time to Conflict Point and Pedestrian Time to Conflict Point) and the distance-related measures (Vehicle longitudinal distance to Conflict Point and Pedestrian Lateral distance to Conflict Point) affect the deceleration rate choice, the drivers‘ effective decelerating zone with sight angle has been proposed with the consideration of longitudinal & lateral conflict behavior. Minimum Vehicle-Pedestrian conflict distance is calculated and a 2 m minimum distance is suggested as the threshold for collision discrimination. Comparisons which address the needs to make the intercultural adaptation when introducing Driver Assistance Systems to developing countries have also been made to show the significant differences between China and Germany. The whole work could hopefully be the groundwork in the target of conflict pre-scanning by decelerating zones under various conflict situations and the design of vehicle active safety systems.

Injured probability assessment in frontal pedestrian-vehicle collision counting uncertainties in pedestrian movement

In probabilistic approaches, where uncertainties in pedestrian motion are counted, the distance model is important for the accurate and robust collision risks evaluation. Focusing on the typical frontal pedestrian-vehicle collision, the conflict distance model with the merit to distinguish front impacts from side ones is presented. Based on stochastic pedestrian model and Unscented Transformation (UT) method, the time-to-collision (TTC) and conflict distance are sampled, and their probability density functions (pdf) as well as the collision probability are deduced. The presented distance model and probabilistic method are verified with Monte Carlo (MC) as the reference, and show the high accuracy and potential for real-time application. Utilizing the estimated collision speed and its probability distribution, a unified model assessing the injured probabilities of pedestrian in front collision is proposed. A pedestrian-vehicle conflict scenario is constructed to evaluate the effectiveness of the probabilistic injury assessment. Simulation results show that the proposed method is sensitive to evasive maneuvers, and provides more useful cues for the optimization of collision avoidance control than the deterministic approaches.

Simulated interactions of pedestrian crossings and motorized vehicles in residential areas

To evaluate whether motorized vehicles can travel through a residential area, this paper develops a cellular automata (CA) model to simulate the interactions between pedestrian crossings and motorized vehicles in a residential area. In this paper, pedestrians determine their crossing speed according to their judgments of the position and velocity of the upcoming vehicles. The pedestrians may walk slowly or quickly or even run, and the pedestrian crossing time influences the vehicle movement. In addition, the proposed model considers the safety margin time needed for pedestrians to cross, and pedestrian–vehicle conflict is considered using the vehicle collision avoidance rule. Through simulations of interactions of pedestrian crossings with motorized vehicles’ movement on a typical road in a residential area, the average wait time for pedestrians to cross and the average vehicle velocity under different pedestrian crossing volumes, different vehicle flows and different maximum vehicle velocities are obtained. To avoid an excessive waiting time for pedestrians to cross, the vehicle flow should be less than 180 veh/h, which allows an average of less than 10 s of waiting time; if the vehicle flow rate is less than 36 veh/h, then the waiting time is approximately 1 s. Field observations are conducted to validate the simulation results.

Quantitative analysis of pedestrian safety at uncontrolled multi-lane mid-block crosswalks in China

A lot of pedestrian-vehicle crashes at mid-block crosswalks severely threaten pedestrian’s safety around the world. The situations are even worse in China due to low yielding rate of vehicles at crosswalks. In order to quantitatively analyze pedestrian’s safety at multi-lane mid-block crosswalks, the number of pedestrian-vehicle conflicts was utilized to evaluate pedestrian’s accident risk. Five mid-block crosswalks (Wuhan, China) were videoed to collect data of traffic situation and pedestrian-vehicle conflicts, and the quantity and spatial distribution of pedestrian-vehicle conflicts at multi-lane mid-block crosswalk were analyzed according to lane-based post-encroachment time(LPET). Statistical results indicate that conflicts are mainly concentrated in lane3 and lane6. Percentage of conflict of each lane numbered from 1 to 6 respectively are 4.1%, 13.1%, 19.8%, 8.4%, 19.0%, 28.1%. Conflict rate under different crossing strategies are also counted. Moreover, an order probit (OP) model of pedestrian-vehicle conflict analysis (PVCA) was built to find out the contributions corresponding to those factors (such as traffic volume, vehicle speed, pedestrian crossing behavior, pedestrian refuge, etc.) to pedestrian-vehicle conflicts. The results show that: pedestrian refuge have positive effects on pedestrian safety; on the other hand, high vehicle speed, high traffic volume, rolling gap crossing pattern, and larger pedestrian platoon have negative effects on pedestrian safety. Based on our field observation and PVCA model, the number of conflicts will rise by 2% while the traffic volume increases 200 pcu/h; similarly, if the vehicle speed increases 5km/h, the number of conflicts will rise by 12% accordingly. The research results could be used to evaluate pedestrian safety at multi-lane mid-block crosswalks, and useful to improve pedestrian safety by means of pedestrian safety education, pedestrian refuge setting, vehicle speed limiting, and so on.

Analysis of drivers’ performance in response to potential collision with pedestrians at urban crosswalks

Protection of vulnerable road users has been an increasingly important requirement for today's autonomous vehicles. Analysis of drivers’ response to potential collision with pedestrians can provide guidance for vehicle evasive manoeuvre and data support for traffic collision modelling. Field traffic data were collected by video recording and image processing at urban midblock crosswalks in Beijing, China and Munich, Germany. The drivers’ response to vehicle–pedestrian conflict is discussed by deceleration and acceleration phases considering the lane-based kinematics of vehicles. Some basic characteristics describing the driver behaviour in an evasive process are statistically analysed, including the yielding decision, space history of deceleration, deceleration rate choice, and accelerating behaviour. Results show significant differences in drivers’ yielding decisions. In addition, the onset of braking and the trend of the space history of average deceleration rate during the drivers’ approaching process have been quantitatively proposed. The contributing factors to driver's yielding behaviour are analysed by the Binary Logit Model. The behavioural differences address the needs to make intercultural adaptation when introducing new autonomous vehicle technologies to developing countries. This study provides a basis for establishing evasive decision corrections for drivers or driverless vehicles.

Specification and calibration of a microscopic model for pedestrian dynamic simulation at signalized intersections: A hybrid approach

Macroscopic pedestrian models for bidirectional flow analysis encounter limitations in describing microscopic dynamics at crosswalks. Pedestrian behavior at crosswalks is typically characterized by the evasive effect with conflicting pedestrians and vehicles and the following effect with leading pedestrians. This study proposes a hybrid approach (i.e., route search and social force-based approach) for modeling of pedestrian movement at signalized crosswalks. The key influential factors, i.e., leading pedestrians, conflict with opposite pedestrians, collision avoidance with vehicles, and compromise with traffic lights, are considered. Aerial video data collected at one intersection in Beijing, China were recorded and extracted. A new calibration approach based on a genetic algorithm is proposed that enables optimization of the relative error of pedestrian trajectory in two dimensions, i.e., moving distance and angle. Model validation is conducted by comparison with the observed trajectories in five typical cases of pedestrian crossing with or without conflict between pedestrians and vehicles. The characteristics of pedestrian flow, speed, acceleration, pedestrian-vehicle conflict, and the lane formation phenomenon were compared with those from two competitive models, thus demonstrating the advantage of the proposed model.

Probabilistic risk assessment for pedestrian–vehicle collision considering uncertainties of pedestrian mobility

ABSTRACTObjectives: The uncertainties of pedestrian mobility are important factors affecting the accuracy and robustness of an active pedestrian protection system. This study is to provide the means for probabilistic risk evaluation of pedestrian–vehicle collision by counting the uncertainties in pedestrian motion.Method: The pedestrian is modeled by a first-order Markov model to characterize the stochastic properties in mobility according to field experiments of pedestrians crossing an uncontrolled road. Based on the assumption of Gaussian distribution, unscented transformation (UT) is employed to predict the collision risk probability with the symmetric σ-set constructed on the basis of discrete trajectory simulation. Simulation experiments were carried out with 10,000 Monte Carlo (MC) simulations as the reference.Results: The probability density distributions of time-to-collision, minimal distance, and collision probability estimated by UT coincide with the reference ones under various vehicle–pedestrian conflict scenarios, and the maximal deviation of collision probability from the reference is 5.33%. The UT method is about 600 times faster than the MC method (10,000 runs), which means that the proposed method has the potential for online application.Conclusions: This article presents an effective and efficient algorithm to estimate the collision probability by using a UT method to solve the nonlinear transformation of uncertainties in pedestrian motion. Simulation results show that the UT-based method achieves accurate collision probability estimation and higher computation efficiency than MC and provides more valuable information concerning collision avoidance than the deterministic methods in the design of a pedestrian collision avoidance system.

Surrogate Safety Analysis of Pedestrian-Vehicle Conflict at Intersections Using Unmanned Aerial Vehicle Videos

Conflict analysis using surrogate safety measures (SSMs) has become an efficient approach to investigate safety issues. The state-of-the-art studies largely resort to video images taken from high buildings. However, it suffers from heavy labor work, high cost of maintenance, and even security restrictions. Data collection and processing remains a common challenge to traffic conflict analysis. Unmanned Aerial Systems (UASs) or Unmanned Aerial Vehicles (UAVs), known for easy maneuvering, outstanding flexibility, and low costs, are considered to be a novel aerial sensor. By taking full advantage of the bird’s eye view offered by UAV, this study, as a pioneer work, applied UAV videos for surrogate safety analysis of pedestrian-vehicle conflicts at one urban intersection in Beijing, China. Aerial video sequences for a period of one hour were analyzed. The detection and tracking systems for vehicle and pedestrian trajectory data extraction were developed, respectively. Two SSMs, that is, Postencroachment Time (PET) and Relative Time to Collision (RTTC), were employed to represent how spatially and temporally close the pedestrian-vehicle conflict is to a collision. The results of analysis showed a high exposure of pedestrians to traffic conflict both inside and outside the crosswalk and relatively risking behavior of right-turn vehicles around the corner. The findings demonstrate that UAV can support intersection safety analysis in an accurate and cost-effective way.

Studying critical pedestrian behavioral changes for the safety assessment at signalized crosswalks

Pedestrian-vehicle conflicts are one of the most important safety concerns at signalized intersections especially in urban areas. Conflicting vehicles and pedestrians select their maneuvers by predicting the other user behavior. Sudden behavioral changes of pedestrians such as sudden speed change (acceleration or deceleration) cannot be predicted by drivers, which can lead to safety hazards especially if these sudden behavioral changes occur near conflict areas. In this study, continuous pedestrian speed profiles were analyzed at signalized crosswalks to investigate the existence of such behavioral changes. A methodology is proposed to identify significant sudden changes of pedestrian speeds. The locations and timings of these sudden speed change events were analyzed, and the influencing factors such as crosswalk geometry and signal timing were studies and evaluated. Five signalized crosswalks at three intersections in Nagoya City were videotaped for analysis. Individual pedestrian maneuvers were extracted with image processing software. Empirical analysis showed that sudden acceleration events were observed at the entrance points to the pedestrian-vehicle conflict area, which highlights the significance of these events to pedestrian-vehicle conflict analysis. A multinomial logit model was developed to estimate the probability of a pedestrian making a sudden speed change as a function of different influencing factors. The results implied that the entering speed, necessary speed to finish crossing before the onset of the pedestrian signal red phase, and crosswalk length have a significant impact on speed change choices. This paper presents important suggestions to understanding pedestrian maneuvers in detail from the viewpoint of safety.

Evaluation of Pedestrian–Vehicle Conflict Severity at Unprotected Midblock Crosswalks in India

Promoting and creating proper facilities for nonmotorized (pedestrian and bicycle) trips is very important in an urban transportation system to enhance pedestrian safety. Pedestrian–vehicle conflicts on urban roads are increasing, particularly at road crossings, because of the tremendous rate of growth in vehicle traffic in developing countries. Accident statistics clearly indicate the need to improve pedestrian safety and to analyze the pedestrian–vehicle interactions and collisions more deeply. This study analyzed the severity of pedestrian–vehicle conflicts at unprotected midblock crosswalk locations under mixed traffic conditions. The pedestrian–vehicle conflicts were considered on the basis of a pedestrian safety margin, which can be defined as the time difference between the time gap of an approaching vehicle and the pedestrian crossing time. For this purpose, field surveys were conducted at eight unprotected midblock crosswalk locations. Data such as pedestrian demographics and behavioral, traffic, vehicle, and roadway characteristics were considered to analyze the severity of the pedestrian–vehicle conflicts. The study identified the significant contributing factors in such conflicts by using an ordered probit model. The model’s results show that rolling behavior, pedestrian speed change condition, land use type, and vehicle speed have a significant effect on the severity of pedestrian–vehicle conflicts. The findings of this study contribute to developing traffic countermeasures to reduce the severity of pedestrian–vehicle conflict levels in order to improve pedestrian safety at unprotected midblock crosswalk locations under mixed traffic conditions. More studies at various unprotected midblock crosswalk locations would be useful to develop guidelines for redesigning the existing midblock crosswalk facilities by introducing suitable traffic control measures.

A study on crossing speed profiles of pedestrians at signalized crosswalks

Pedestrian–vehicle conflicts are one of the most important safety concerns especially at intersections. Of total traffic fatalities, 30% and 36% are pedestrians in Qatar and in Japan, respectively (National Police Agency in Japan, 2015). Although pedestrians at signalized intersections are given priority during the green phase, turning vehicles in conflict often do not give the right of way to pedestrians but tend to compete for it. Furthermore, long crosswalks, short green times, and other reasons may cause pedestrians to rush or suddenly change their speed without paying attention to the surrounding conditions (Iryo-Asano et al. 2014). The sudden changes in pedestrian behavior while crossing cannot be predicted by the driver, which can cause severe conflicts. Therefore, the possible behavioral changes of pedestrians should be studied so that surrogate safety measures such as post-encroachment time can be quantitatively estimated to provide a reliable assessment of pedestrian–vehicle conflicts and their severities. Continuous pedestrian speed profiles were analyzed at signalized crosswalks considering the impact of crosswalk geometry and signal timing. Five signalized crosswalks at three intersections in Nagoya City were videotaped and individual pedestrian maneuvers were extracted by image processing. A stepwise speed function is proposed to identify significant sudden changes in individual pedestrian speed profiles. The locations and timings of these sudden speed change events were analyzed, and the influencing factors were statistically evaluated. Empirical analysis showed that sudden acceleration events were observed at the entrance points to the pedestrian–vehicle conflict area, which highlights the significance of these events to pedestrian–vehicle conflict analysis. More than a quarter of all acceleration events occurred just after the onset of the pedestrian flashing green signal indication. Furthermore, it is concluded that long crosswalks have higher percentage of speed change occurrence and as a result higher risk of crashes. In this regard, the application of two-stage pedestrian crossing is a potential solution to reduce crosswalk length and the possibility of having unpredicted pedestrian behavioral changes. In general, the results implied that pedestrian entering speed to crosswalk, necessary speed to finish crossing before the onset of the pedestrian red signal indication, and crosswalk length have a significant impact on pedestrian speed change choices.

Analyses of pedestrian behavior on mid-block unsignalized crosswalk comparing Chinese and German cases

A large number of pedestrian fatalities are caused by the vehicle-pedestrian accidents. The application of new theory and technological approaches may hold great potential to reduce the accident frequency and severity for pedestrians. Considered the different driving cultures between China and Germany, the adaptation of such application in new market triggers an “intercultural comparison” related to the road user behavior and traffic safety. Field traffic data have been collected by video recording and image processing at unsignalized mid-block crosswalks both in Beijing, China and Munich, Germany. Centered Vehicle-Pedestrian conflict situation, pedestrian speed performance in different pedestrian categories and walking phases, pedestrian waiting behavior related to waiting decision choice and waiting time, pedestrian gap acceptance were statistically analyzed for understanding the pedestrian behavior in the conflict process. Intercultural comparisons were made between China and Germany. The research results addressed how the conflict participants (pedestrians only) behave differently and would hopefully be the impetus for further intercultural analyses from urban traffic side.

Quantitative analysis of lane-based pedestrian-vehicle conflict at a non-signalized marked crosswalk

Pedestrian-vehicle conflict is a common and dangerous event which occurs in both urban and rural areas in developing countries. Lane-based evaluation of pedestrian-vehicle conflict is still an open research topic in the traffic safety, urban planning, and city government communities. A lane-based approach for evaluating the post-encroachment time between pedestrians and vehicles was proposed. This study analyzed the lane-based distribution of pedestrian-vehicle conflict using collected video data which recorded the behaviors of vehicles and pedestrians in a non-signalized marked crosswalk in Wuhan, China, and discussed the effect of waiting time on lane-based pedestrian-vehicle conflict as well as the distribution of pedestrian walking speed under different levels of severity of lane-based pedestrian-vehicle conflict. Experimental results showed that shorter waiting times and smaller waiting areas are very strongly related to lane-based conflict, but that walking speed is not a significant factor in lane-based pedestrian-vehicle conflict.

Safety assessment of pedestrian crossing solutions

Paper presents preliminary findings from the research project Mobis which is aimed at developing a method of assessing safety of pedestrian road crossings by using video image analysis. Pedestrian and vehicle traffic has been recorded at a selected crossing site in Warsaw for 2 months, before and after installation of safety measures which included active signage and speed humps. Speeds of approaching vehicles were measured and vehicle-pedestrian conflict situations identified by using video analysis. Results indicate that both SignFlash active signage and speed humps reduce mean vehicle speed and have a positive impact on drivers’ behaviour.