To predict the probability of roadside accidents for curved sections on highways, we chose eight risk factors that may contribute to the probability of roadside accidents to conduct simulation tests and collected a total of 12,800 data obtained from the PC-crash software. The chi-squared automatic interaction detection (CHAID) decision tree technique was employed to identify significant risk factors and explore the influence of different combinations of significant risk factors on roadside accidents according to the generated decision rules, so as to propose specific improved countermeasures as the reference for the revision of the Design Specification for Highway Alignment (JTG D20-2017) of China. Considering the effects of related interactions among different risk factors on roadside accidents, path analysis was applied to investigate the importance of the significant risk factors. The results showed that the significant risk factors were in decreasing order of importance, vehicle speed, horizontal curve radius, vehicle type, adhesion coefficient, hard shoulder width, and longitudinal slope. The first five important factors were chosen as predictors of the probability of roadside accidents in the Bayesian network analysis to establish the probability prediction model of roadside accidents. Eventually, the thresholds of the various factors for roadside accident blackspot identification were given according to probabilistic prediction results.

In order to strengthen the safety of highway roadsides, it is necessary to take targeted measures according to the roadside hazards, so there is an urgent need to develop research on risk evaluation of highway roadside accidents. Based on accident simulation analysis and the form of accident after vehicles run to the roadside, the rollover risk of roadside accident is classed into four grades, namely, no departure from the ground, slight departure from the ground, one or two turnovers, and more than two turnovers. The factors involved in the causes of roadside accidents of different rollover risks are studied, and the thresholds of driving speed, sideslope gradient, and sideslope height are given. A Bayesian network for risk evaluation of roadside accidents is constructed. Based on the factor thresholds for the causes of roadside accidents, the calculation methods of the probability of different rollover risks of roadside accidents are carried out according to a single factor, two factors, and three factors. The typical cases of roadside accidents are analyzed and the calculation results of the Bayesian network show that the probability of one or two turnover accidents is 0.939, which is consistent with the results of roadside accident simulation tests, proving the accuracy of the risk evaluation methods for highway roadside accidents.

Lane-changing behaviour is one of the complex driving behaviours. The lane-changing behaviour of drivers may exacerbate congestion, however driver behavioural characteristics are difficult to accurately acquire and quantify, and thus tend to be simplified or ignored in existing lane-changing models. In this paper, the Bik-means clustering algorithm is used to analyse the urban road congestion state discrimination method. Then, simulated driving tests were conducted for different traffic congestion conditions. Through the force feedback system and infrared camera, the data of driver lane-changing behaviours at different traffic congestion levels are obtained separately, and the definitions of the start and end points of a vehicle changing lanes are determined. Furthermore, statistical analysis and discussion of key feature parameters including driver lane-changing behaviour data and visual data under different levels of traffic congestion were conducted. It is found that the average lane-change intention times in each congestion state are 2 s, 4 s, 6 s and 7 s, while the turn-signal duration and the number of rear-view mirror observations have similar patterns of change to the data on lane-changing intention duration. Moreover, drivers’ pupil diameters become smaller during the lane-changing intention phase, and then relatively enlarge during lane-changing; the range of pupil variation is roughly 3.5 mm to 4 mm. The frequency of observing the vehicle in front of the target lane increased as the level of congestion increased, and the frequency of observation in the driver's mirrors while changing lanes approximately doubled compared to driving straight ahead, and this ratio increased as the level of congestion increased.

The paper proposes a model of mandatory lane-changing behaviour based on a non-cooperative game in a traditional environment and analyses its applicability in a connected environment. In order to solve the problem of traffic safety and traffic congestion caused by mandatory lane-changing on urban roads, this paper applies the non-cooperative game theory to describe the game behaviour of the two parties, the lane-changing vehicle and the vehicle behind the target lane, in the connected and traditional environments respectively, and constructs the model considering the safety gain, speed gain and lane-changing gain to obtain a game model and the Nash equilibrium solution. The model is calibrated and tested using NGSIM data, and the results of the study show that the model has a good performance for the decision behaviour of lane-changing vehicles and lag vehicles for mandatory lane-changing behaviour on urban roads.

Frequent and serious traffic accidents have become a focal issue because they hinder the sustainable development of society. In China, roadside accidents account for 40% of fatalities resulting from traffic accidents. Roadside safety has become an important issue of traffic management departments worldwide, and performing research on roadside safety contributes to improving the level of road safety and reducing the number of traffic accidents and fatalities. By systematically sorting a large number of relevant studies, this paper analyzed the current development trends of roadside safety in terms of three aspects (i.e., the year of publication, the country of publication, and the source of publication) and then summarized the research status, existing gaps, and future development directions of roadside safety in terms of three aspects: the frequency of roadside accidents, the severity of roadside accidents, and the practice of roadside safety design. This paper reviewed the different prediction methods and evaluation models for the frequency and severity of roadside accidents. According to the number of times mentioned in the literature, the first five significant risk factors that cause frequent roadside accidents are small-radius curves, heavy traffic, objects adjacent to the lane (such as poles and trees), narrow lanes, and narrow shoulders, and the first five significant risk factors that cause fatal roadside accidents are driver age ≤25 or ≥65, alcohol, speeding, failure to use seat belts, and heavy trucks. Future research on the frequency and severity of roadside accidents should focus on quantitatively analyzing the probability of roadside accidents and occupant injury risk and developing methods for identifying roadside accident blackspots. For roadside safety design, roadside clear zones and safety slopes should be precisely quantified based on a cost-benefit analysis in future studies.

Auxiliary lanes on two-lane highway are lanes setting on the right side of highway for the slow vehicles, and they can provide safe overtaking chances for cars using the original lane instead of the opposite lane. Based on the principle that the net benefit is greater than zero, the calculation model of the minimum spacing of auxiliary lanes on two-lane highway is established. After calibrating the model parameters, recommended minimum spacing values for auxiliary lanes are given corresponding to different highway classes, design speeds, and terrains. Based on traffic simulation data, the relationship model is established among the length of auxiliary lane section with uniform widths, traffic volumes, and driving speeds. By analyzing the design capacity of two-lane highway, suggestion values of the length of auxiliary lane section with uniform widths are given for two-lane highway with different design speeds and terrains. Based on driving safety and questionnaire survey on lateral vehicle spaces, calculation formula and suggestion values are presented for the width of auxiliary lanes on two-lane highway.