What will the car driver do? A video-based questionnaire study on cyclists' anticipation during safety-critical situations

A modeling method for two-dimensional two-wheeler driving behavior during severe conflict interaction at intersections

The safety of two-wheelers is a serious public safety issue nowadays. Two-wheelers usually have severe conflict interaction with vehicles at intersections, such as running red lights, which is very likely to cause traffic accidents. Therefore, a model of two-wheeler driving behavior in conflicting interactions can provide guidance for traffic safety management on one hand, and can be used for the development and testing of autonomous vehicles on the other. However, the existing models perform poorly when interacting with vehicles. To address the problems, this paper proposes a modeling method (an improved social force model, ISFM) for two-dimensional two-wheeler driving simulation for conflict interaction at intersections. Based on analysis of naturalistic driving study data, when two-wheelers encounter with vehicles, their driving intentions and trajectories can be categorized into two groups, which are yielding and overtaking. Therefore, the vehicle-related social forces are designed to be a set of two forces rather than a repulsion force in original SFM, which is a yielding force based on the relative distance between the two-wheeler and the vehicle, and an overtaking force based on the velocity of the two-wheeler itself. This opens up the possibilities for modeling the multi-modal driving intention of two-wheelers encountering with cross traffic. Based on ISFM, a bicycle model, a powered two-wheeler (PTW) model and a model of a group of PTWs, are then constructed. Compared to the original SFM, ISFM increases the precision of driving intention prediction by 19.7 % (yielding situation) and 25.0 % (overtaking situation), and reduces the root mean square error between simulated and actual trajectories by 7.8 % and 14.8 % on the bicycle model and the PTW model, respectively. Meanwhile, the model of a group of PTWs also performs well. Finally, the results of ablation experiments also validate the effectiveness of the social force designed based on velocity.

Development of a hazard prediction test for Chinese cyclists and its association with crash involvement

Introduction

Hazard perception is the ability to sense the road environment and predict and respond to the upcoming dangerous events, and this factor is closely related to cyclists' crash involvement. However, due to a lack of valid instruments, studies concerning the hazard predictions and crashes of cyclists in China remain limited. This study attempted to develop a hazard prediction test for cyclists.

Method

The experiment presented 44 video clips filmed from cyclists' perspectives to 61 children aged 13-16 years and 119 adults aged 18-30 years. After the video clip displayed a black screen, participants were asked to answer the following questions: "What is the hazard?" (question 1), "Where is the hazard?" (question 2), and "What happens next?" (question 3). The differences in test scores between cyclists with high and low levels of experience, cyclists of different ages, and crash-involved and noncrash-involved cyclists were compared to examine the validity of the test.

Results

The final test contained 21 video clips and the internal consistency reliabilities of the three questions were satisfactory. Experienced cyclists are better able to identify and predict hazards than are cyclists with less experience, and adult cyclists have better hazard prediction abilities than child cyclists. More importantly, crash-involved cyclists receiving lower scores with respect to their ability to identify and predict hazards than noncrash-involved cyclists, thus indicating that the discriminant validity of the test was acceptable.

Practical applications

This newly-developed test exhibits acceptable reliability and validity and can be used as an effective tool to measure the hazard prediction abilities of cyclists with different ages and levels of experience in China. The natural driving videos and test in the study may hold promise for future practical applications, and the implications for road safety are discussed.

Parental Assessment of Benefits and of Dangers Determines Children's Permission to Play Outdoors

During the early years, children's outdoor play is dependent on parental supervision. Parents' perceptions are likely to influence what the child is permitted to do. To better understand the involved mechanisms in parents' decision making in such contexts, an online photo-based questionnaire was administered. The tool investigates, in different situations, parents and their children's experience, parents' perceptions, and permission to play. A total of 417 parents of children aged from 1.5 and 6.0 completed the questionnaire. Results showed that parents, overall, have a positive attitude towards outdoor play. Main concerns were about risk of injury but in most cases, perceived benefits outweigh perceived dangers. "Sawing wood" was the only situation with a negative benefits/dangers balance. A linear regression analysis revealed that permission to play outdoors is based on parental assessment of benefits and dangers. Perceived benefits appeared to have more influence on parental decision than perceived dangers, while perceived competence had only a small influence. The results also showed that parents' childhood experience of outdoor play was an important determinant for adults' perceptions, perhaps demonstrating intergenerational concerns, as outdoor play is in decline. To overcome a negative intergenerational effect on children's outdoor play, interventions and communication should focus on associated benefits.

Cycling Skill Inventory: Assessment of motor-tactical skills and safety motives

Objective: It is well established within the traffic psychology literature that a distinction can be made between driving skill and driving style. The majority of self-report questionnaires have been developed for car drivers, whereas only limited knowledge exists on the riding skill and style of cyclists. Individual differences in cycling skills need to be understood in order to apply targeted interventions.Methods: This study reports on a psychometric analysis of the Cycling Skill Inventory (CSI), a self-report questionnaire that asks cyclists to rate themselves from definitely weak to definitely strong on 17 items. Herein, we administered the CSI using an online crowdsourcing method, complemented with respondents who answered the questionnaire using paper and pencil (n = 1,138 in total). Our analysis focuses on understanding the major sources of variance of the CSI and its correlates with gender, age, exposure, and self-reported accident involvement as a cyclist.Results: The results showed that 2 components underlie the item data: Motor-tactical skills and safety motives. Correlational analyses indicated that participants with a higher safety motives score were involved in fewer self-reported cycling accidents in the past 3 years. The analysis also confirmed well-established gender differences, with male cyclists having lower safety motives but higher motor-tactical skills than female cyclists.Conclusions: The nomological network of the CSI for cyclists is similar to that of the Driving Skill Inventory for car drivers. Safety motives are a predictor of self-reported accident involvement among cyclists.