A Driving Simulator Based Study On The Optimization Of Signs And Markings And The Warning System Design Method For Grade Crossings

The potential severities of grade crossing collisions make them a common problem in the railway and road transportation system.Drivers as the main participant involved in the driving task,drivers' improper behavior is the main cause of grade crossing accidents.The traffic signs and pavement markings for grade crossing are the basic elements of grade crossings,and the effective communication of their information is the basis for ensuring the safety of grade crossings.Meanwhile,the development of active warning technology provides a novel low-cost method for improving the safety of grade crossings.This study proposed a more reasonable design and placement of signs and markings for China(PSM),and on this basis,proposed reasonable and efficient in-vehicle audio warning programs(IVAW).It is assumed that the mutual assistance of these two countermeasures can be used to improve the reliability and real-timeless of the grade crossing warning system.Based on the driving simulation platform,the effectiveness of warning system on driver behavior at grade crossing was verified.This study provides important theoretical basis and scientific support for the design of traffic signs and markings for grade crossing and the development of intelligent warning technology.The main research did in this thesis were:(1)Optimization of traffic signs and pavement markings for grade crossing,and research on warning system design method.This study research the design and placement of signs and markings for grade crossing from the traffic control device of grade crossing and the driving phase of grade crossing approach zone.Combined with literature summary and questionnaire survey to clarify the key design issues of traffic signs and markings for grade crossing in China.And this study improved the design of 2 existing signs,and supplemented the design of 1 prohibition sign,7 warning signs,1 auxiliary sign,and 1 pavement marking to improve the China's traffic signs and markings system for grade crossing.Based on the theory of grade crossing approach zone,the corresponding placement requirements of signs and markings for different control types and special situations grade crossing were proposed.On this basis,phased IVAW programs were proposed for yield controlled grade crossings,stop controlled grade crossings,and flashing-light controlled grade crossings to remind drivers to take corresponding collision avoidance measures.The warning system would determine different warning timings and contents according to different driving stages in the approach zone and different train states.(2)Effect of warning system on approach behavior at yield controlled grade crossings.This study considered foggy factors and train status to test the effectiveness of yield controlled grade crossings warning system under different conditions.The drivers' approach speed control behavior and deceleration behavior were analyzed firstly using the mixed linear model.Finally,results of the post experiment questionnaire were analyzed.Results indicated that more drivers tended to slow down to avoid a collision with the influence of warning system.PSM and IVAW both could help drivers start the deceleration actions earlier,approach the grade crossing at a lower speed,and make the braking process is more stable.Drivers' behavior improved less in clear condition.But in fog,the warning system could help drivers take deceleration measures as soon as possible,make drivers' brake jerks,maximum decelerations and average decelerations basically the same as when it is sunny,which greatly eased drivers' braking intensity in foggy weather.As for gender,PSM had the same safety protection effect for male drivers and female drivers,while the impact of IVAW on male drivers is more obvious.The warning system could reduce the gender differences on driver behavior.As for vocation,the two safety countermeasures had similar effects on professional and non-professional drivers' behavior.In addition,the results of the questionnaire showed that drivers' subjective recognitions of PSM and IVAW were well,and the effect of IVAW in fog was better than that in no fog.(3)Effect of warning system on approach behavior at stop controlled grade crossings.This study also considered foggy factors and train status to test the effectiveness of stop controlled grade crossings warning system on driving behavior.The drivers' approach speed control behavior,collision avoidance behavior and compliance behavior were analyzed using the mixed linear model,hierarchical tree-based regression model and the binary logistic regression model.Results indicated that PSM could help driver make the brake decision earlier and improve the speed control performance.However,it had no effect on driver's collision avoidance pattern,wait or not,and compliance.The warning system could significantly improve drivers' speed control behavior,collision avoidance pattern and compliance behavior,and reduce drivers' potential risk to a greater extent.The warning system greatly increased drivers' compliance in fog when the train status is 4s,7s and 10 s.As for gender,the effect of warning system on male drivers was more significant,shortening the behavior difference between female drivers and female drivers.In addition,the percentage of drivers' complete stopping and waiting for the train at the stop controlled crossing were higher than that of yield controlled grade crossing.Drivers' understanding and behavior at the two signs are different.However,the compliance rate of stop sign under the influence of warning system was only 57.25%.Therefore,the application of stop sign at grade crossings still needs further research and consideration.(4)Effect of warning system on approach behavior at flashing-light controlled grade crossings.This study designed five flashing red light trigger timings and two foggy factors.Based on the obtained driving behavior data,two typical behavioral variables that can be used to evaluate the safety of flashing-light controlled grade crossings were collected from driving simulator experiment data,such as approaching speed and compliance.A conceptual model was developed which divided the stop/go process into three successive stages,i.e.approach stage,reaction stage and action stage.The driving performance at each stages and stopping behavior were analyzed.The analysis method concluded the mixed linear model,hierarchical tree-based regression model and the binary logistic regression model.The analysis results showed that PSM could offer limited safety benefits on speed control performance at approach stage,while no effect on drivers' stopping decision and action.Warning system could help drivers to make deceleration decision earlier,shorten drivers' brake reaction time,reduce the maximum deceleration and increase their speed adjustment time.Thereby further improving the drivers' compliance rate and specific stopping performance,making the entire braking process more stable.Foggy factors have no significant effect on the compliance rate,but drivers' braking in fog were more intense.The warning system could eliminate the adverse effects of heavy fog.Compared with female drivers,male drivers were more likely to violate the flashing light.Especially in the case of earlier FLTT,gender was a key demographic variable in influencing compliance rate.The warning system could reduce the difference in performance between male and female to a certain extent.