Spatial-temporal analysis of pedestrian injury severity with geographically and temporally weighted regression model in Hong Kong

This study intended to (1) investigate the pedestrian injury severity involved in traffic crashes; and (2) address the spatial and temporal heterogeneity simultaneously. To achieve the objectives, geographically and temporally weighted regression (GTWR) model was proposed to deal with both spatial and temporal heterogeneity simultaneously. The pedestrian crash data of Hong Kong metropolitan area from 2008 to 2012 were collected, involving 1652 pedestrian-related injury samples. By comparing GTWR model and standard geographically weighted regression (GWR) model and temporally weighted regression (TWR) model, the proposed GTWR model showed potential benefits in modeling both spatial and temporal non-stationarity simultaneously in terms of goodness-of-fit and F statistics. Results revealed that number of vehicles, number of pedestrian-related casualties, speed limit, vehicle movement and injury location have significant influence on pedestrian injury severity in different areas. The conclusions are reached that GRWR model can address the relationship between pedestrian injury severities and influencing factors, as well as accommodating spatial and temporal heterogeneity simultaneously. The findings provide useful insights for practitioners and policy makers to improve pedestrian safety.     

Lessons learned from pedestrian-driver communication and yielding patterns

Understanding the hidden patterns of tacit communication between drivers and pedestrians is crucial for improving pedestrian safety. However, this type of communication is a result of the psychological processes of both pedestrians and drivers, which are very difficult to understand thoroughly. This study utilizes a naturalistic field study dataset and explores the hidden patterns from successful and failed communication events using a pattern recognition method known as Taxicab Correspondence Analysis (TCA). The successful communication scenarios indicate the combinations of variable attributes such as eye contact, facial expression, the assertion of crossing, and effective traffic control devices are strongly associated with successful scenarios. The patterns for failed scenarios are most likely to be on the roadway with a relatively higher speed limit (e.g., 35 mph) and a relatively lower speed limit (e.g., 15 mph) under different conditions. On roadways with a higher speed limit, the failed scenarios are highly associated with passive and undecisive pedestrians, pedestrians far away from the crosswalk, regardless of pedestrian-driver eye contact and facial expression of the pedestrians. Instead of waiting for pedestrians to making a crossing decision, overspeeding drivers are more likely to speed up and pass the crosswalk. On roadways with a lower speed limit, the failed scenarios are often associated with distracted pedestrians, vehicles having the right of way, and the absence of effective traffic control devices. These findings could help transportation agencies identify appropriate countermeasures to reduce pedestrian crashes. The findings on driver-pedestrian communication patterns could provide scopes for improvement in computer vision-based algorithms designed for autonomous vehicle industries.     

Pedestrians’ road crossing behaviour in front of automated vehicles: Results from a pedestrian simulation experiment using agent-based modelling

The objective of this research is to explore the relation between personal characteristics of pedestrians and their crossing behaviour in front of an automated vehicle (AV). For this purpose, a simulation experiment was developed using Agent-Based Modelling (ABM) techniques. Sixty participants were asked to cross the road in a virtual environment displayed on a computer screen, allowing to record their crossing behaviour when in the presence of AVs and conventional vehicles (CVs). In some experimental configurations, the AVs communicated their intention to continue or not to continue their trajectories through the use of lights. The ABM allowed controlling the behaviour of the vehicles when interacting with the simulated avatar of the respondents. The subjects of the experiment were also asked to fill in a questionnaire about usual behaviour in traffic, as well as attitudes and risk perceptions toward crossing roads. The questionnaire data were used to estimate individual specific behavioural latent variables by means of principal component analysis which resulted in three main factors named: violations, lapses, and trust in AVs. The results of generalized linear mixed models applied to the data showed that besides the distance from the approaching vehicle and existence of a zebra crossing, pedestrians’ crossing decisions are significantly affected by the participants’ age, familiarity with AVs, the communication between the AV and the pedestrian, and whether the approaching vehicle is an AV. Moreover, the introduction of the latent factors as explanatory variables into the regression models indicated that individual specific characteristics like willingness to take risks and violate traffic rules, and trust in AVs can have additional explanatory power in the crossing decisions.     

Attitudes of learner drivers toward safety at level crossings: Do they change after a 360° video-based educational intervention?

In light of the growing number of level crossing accidents and the limited prevention programmes, this study examined relationships among attitudes toward traffic rules, impulsiveness, and behavioural intentions at level crossings. It explored the behavioural effects of an educational programme newly developed within the framework of the Croatian national safety project “Implementation of measures to improve the safety of the most vulnerable traffic participants at level crossings“. The programme aimed to change risky attitudes and behavioural intentions of learner drivers at level crossings. It consists of a safety lecture accompanied by pictures, videos and the exposition to a 3D virtual reality film shot at a real level crossing, which allows the participant to experience, from the driver’s perspective, safe and risky crossings. The programme was implemented in 11 driving schools. First, 285 participants (62.8% men) answered a questionnaire measuring safety attitudes toward traffic and impulsiveness, then they attended a lecture and participated in the virtual reality experience. Finally, they answered a questionnaire measuring planned future behaviour at level crossings. The results showed that attitudes toward level crossing risk significantly predicted intended driving behaviour at level crossings. Furthermore, the 360° video-based educational intervention altered the relationships connecting attitudes toward level crossings and risky driving behaviour at level crossings. The practical implications of these results are discussed.     

Factors explaining driver yielding behaviour towards pedestrians at courtesy crossings

Courtesy crossings are pedestrian crossing facilities where drivers are not legally required to stop for pedestrians, but are encouraged to do so by design elements such as stripes, coloured or textured road surfaces, visual narrowings of the carriageway, and ramps. There is little empirical evidence on drivers' behaviour or guidance on how to design these crossings. This paper analysed data for 937 interactions between drivers and pedestrians at 20 crossings across England, comparing driver yielding behaviour at courtesy crossings and at zebras (marked unsignalised crossings, where drivers are legally required to stop); and identifying the design elements associated with yielding behaviour at courtesy crossings. The analysis controlled for crossing stage; characteristics and situation of pedestrians and vehicles; characteristics of the road and site; and time context. Driver yielding behaviour was analysed for each separate traffic lane that pedestrians need to cross. We found that all four design elements considered (stripes, coloured/textured surface, visual narrowing, and ramps) increased the propensity of the first vehicle to stop and of any vehicle to stop. A before-after analysis then showed that adding a new element (stripes) to a courtesy crossing led to an increase in yielding rates from 20% to 97%. Overall, we found evidence supporting the use of multiple design elements in courtesy crossings. We discuss the implications of these findings for transport policy and urban design.     

Pedestrian detection using a moving camera: A novel framework for foreground detection

While background subtraction techniques have been widely applied to detect moving objects in a video stream captured by a static camera, detecting moving objects using a moving camera still represents a challenging task. In this context, pedestrian detection using a camera placed on the top of a vehicle’s windshield has been rarely investigated. This is mainly due to the background ego-motion. Since the scene captured by the camera seems in motion, it is very difficult to distinguish the moving pedestrians from the others that belong to the static part of the scene. For this reason, a compensation step is needed to suppress the ego-motion. This paper presents a study on the main challenges facing pedestrian detection systems as well as methods proposed to handle these challenges. A novel trajectory classification framework for detecting pedestrians even in challenging real-world environments is proposed. The proposed method models the background motion between two consecutive frames in order to compensate the camera motion. Then, it defines a classification process that differentiates between the background and the foreground in the frame. Using the defined foreground, we consequently identify the presence of pedestrians in the scene. The proposed method was validated on a public benchmark dataset: CVC-14 containing both visible and far infrared video sequences in day and night times. Experimental results confirm the effectiveness of the proposed approach in capturing the dynamic aspect between frames and therefore detecting the presence of pedestrians in the scene.     

An examination of the influence of crosswalk marking removal on pedestrian safety as reflected in road user behaviours

In some local authorities in Israel, road markings were removed from non-signalised crosswalks situated on multilane divided urban roads. This study examined whether this treatment contributes to pedestrian safety, based on the analysis of differences in road user behaviours and pedestrian crossing conditions at sites without crosswalk markings (treatment sites) versus those with the markings (comparison sites). Field observations were conducted at two treatment and four comparison sites, including video-recordings and free-flow speed measurements. The speed data analysis indicated that treatment sites were associated with higher speeds as compared to other sites, at least in one travel direction, and that speed values were sufficiently high to create a threat of severe injury for the crossing pedestrians. Examinations of other road user behaviours showed that treatment sites are associated with higher obedience of pedestrians to safe crossing rules and low rates of pedestrian-vehicle conflicts during the crossing, but also with long waiting times by pedestrians prior to crossing, low rates of giving-way to pedestrians and more vehicles ignoring pedestrian needs to cross. In general, pedestrian crosswalk removal brought about a worsening in the possibility of crossing the road for pedestrians that in combination with high vehicle speeds cannot be recognised as a safety-improving measure. The study did not support the claim that removing a marked crosswalk leads to safety benefits for pedestrians.     

Racial bias in driver yielding behavior at crosswalks

Psychological and social identity-related factors have been shown to influence drivers’ behaviors toward pedestrians, but no previous studies have examined the potential for drivers’ racial bias to impact yielding behavior with pedestrians. If drivers’ yielding behavior results in differential behavior toward Black and White pedestrians, this may lead to disparate pedestrian crossing experiences based on race and potentially contribute to disproportionate safety outcomes for minorities. We tested the hypothesis that drivers’ yielding behavior is influenced by pedestrians’ race in a controlled field experiment at an unsignalized midblock marked crosswalk in downtown Portland, Oregon. Six trained male research team participants (3 White, 3 Black) simulated an individual pedestrian crossing, while trained observers cataloged the number of cars that passed and the time until a driver yielded. Results (88 pedestrian trials, 173 driver-subjects) revealed that Black pedestrians were passed by twice as many cars and experienced wait times that were 32% longer than White pedestrians. Results support the hypothesis that minority pedestrians experience discriminatory treatment by drivers at crosswalks.     

Evaluation of motorized two-wheeler rider responses towards jaywalking pedestrians through mockup control studies for urban streets

This study aims to model the motorized two-wheeler (MTW) riders’ evasive-action behavior towards jaywalking pedestrians using a mockup study. The brake reaction times (BRTs), approach speeds, decelerations, headings, and yaw rates were analyzed for two surprise scenarios (scenarios 1 and 3), one stationary scenario (scenario-2), and one expected scenario (scenario-4). In total, 50 riders participated in the mockup study. The results revealed that the 90th percentile BRT for the expected and surprise scenarios were 3.6 and 1.6 s, respectively. Further, repeated-measures ANOVA was performed followed by mixed effect modeling to ascertain the effect of conflict severity (two groups: group-1 with Time to Collision (TTC) < 1.5 s and group-2 with TTC > 1.5 s) and scenario type (three groups: scenarios 1, 3 and 4) on BRT. The results indicated that the main effects were significant while the interaction effect was not significant. The positive and significant coefficient (0.32) of TTC group-2 indicated higher BRTs than TTC group-1. Considering scenario-1 as the base scenario, the coefficient of scenario 3 (-0.02) indicated that scenario-1 and scenario-3 had a similar effect on BRT, while the coefficient of scenario-4 (1.47) indicated higher BRTs compared to scenario-1. The analysis of evasive action behavior revealed that 32% of riders performed hard braking in surprise scenarios. Further, yaw rate values at the crossing point indicated a loss of control of MTW in 90% of surprise events. The observations from this study provide a basis for developing countermeasures to improve pedestrian and MTW rider safety.     

Revisiting the level-of-service framework for pedestrian comfortability: Velocity depicts more accurate perceived congestion than local density

The evaluation of pedestrian comfortability is important for the construction and management of walkable spaces. Pedestrian level-of-service (LOS), which is mostly categorized by density, has been widely applied and is believed to be capable of indicating the comfortability of the crowd. However, there is a lack of evidence that physically measured LOS reflects psychological comfortability, let alone the comparison between the performances of different candidate indicators, including the velocity and different local densities. Here, we show that walking velocity depicts pedestrian perceived congestion more accurately than density. In our experiments on pedestrians in a room-egress scenario with an inner obstacle, we obtained objective physical trajectory data from video analysis as well as subjective perception data from a questionnaire survey. The performance of the velocity and four types of local densities in reproducing pedestrian perceptions were numerically evaluated. We found that the velocity outperformed the local density. The lower performance of local densities was mainly caused by the pedestrians located at the back of the crowd, who walked at lower velocities and perceived higher congestion, despite their lower local densities that would correspond to less crowdedness from a physical viewpoint. Besides, the perceived congestion of pedestrians was shown to be affected by the initial pedestrian positions at the crowd, the obstacle layout, and the pedestrians’ age and gender. Furthermore, we suggest that the larger the gap between the desired and actual velocities, the larger the extent of the perceived congestion. We expect that our findings will contribute to a more accurate evaluation of pedestrian comfortability, which could help improve the walkable spaces of various infrastructures.