| The road transportation system provides fast,comfortable and convenient service for our daily travel.With the continuous development of urbanization process and the increase of traffic demand,managers have to reconstruct some road segments to expand the traffic capacity.Meanwhile,many existing road networks have experienced serious damage,the decline of road service level and the aging facilities under long-term operation also require road repair.Therefore,the demand for road maintenance grows rapidly in recent years.In the process of road maintenance,managers often separate the activity area from the traffic flow by using specific warning signs and safety protection measures.On the one hand,the existence of work zone leads to a decrease of traffic efficiency.On the other hand,the increase of lane-changing behavior caused by lane closure also brings traffic safety issues.This research aims to investigate driver’s lane-changing behavior in work zone area from the perspectives of micro driving behavior,traffic safety and traffic efficiency.At the same time,this paper also designed an auxiliary audio prompt for guiding merging behavior,and proposed a dynamic signal-based merge strategy with the consideration of queuing length.The effectiveness of the strategy was verified by developing a Cellular Automata simulation.The results can provide some guidance for the traffic organization and management in work-zone related area.The main contents of this paper are as follows:(1)Based on the requirements of technical specifications,the work-zone related test scenarios were established by using driving simulator platform,and the driving simulator experiment was developed to collect drivers’ eye movement and behavioral data.The experiment considered five traffic density levels which range from 20～60pcu/km to simulate different road traffic conditions.At the same time,this paper also proposed an auxiliary audio prompt for guiding merging behavior by sorting out the existing merge strategies.The behavioral characteristics and eye movement characteristics of drivers with and without audio prompt were compared,and four positions for information release were considered,which were 250 m,500m,750 m and1000m upstream of work zone,respectively.(2)Driver’s lane-changing process in work zone was divided into perception stage,preparation stage and action stage.The influence of driver characteristics,traffic density and audio prompt positions on mirco driving behavior in different stages was analyzed.The results showed that male drivers were more sensitive to the road condition changes in work zone area,and they would merge into the open lane earlier than female drivers.In addition,male drivers were more stable in vehicle control during lane changing,which was reflected in lower S.D.of longitudinal velocity and steering wheel velocity.The differences in driving skills and driving experience made professional drivers have more calm driving performance than regular drivers during lane changing,and they always maintained lower S.D.of longitudinal velocity and steering wheel velocity.With the increase of traffic density,the increasing difficulty of lane changing would result in longer duration of preparation stage,and the start point of merging behavior was also closer to the work zone.These would force drivers to accept aggressive driving behavior.The audio prompt was effective in guiding lane-changing behavior.As the warning information was released more in advance,drivers would take merging behavior earlier.(3)The influence of driver characteristics,traffic density and audio prompt positions on eye movement behavior were analyzed in different stages.The results showed that male drivers would pay more attention to the road conditions in the open lane,and their visit duration on the open lane and the side mirror is higher than that of female drivers.In terms of driver profession,professional drivers would pay more attention to the speed-position relationship with the lag vehicle in the open lane since their visit duration on the side mirror was higher than regular drivers.Traffic density had significant impacts on the eye movement behavior.Under low density levels,driver’s visual attention mainly focused on the closed lane to maintain a safe distance with lead vehicle.As traffic density increased,the visual attention gradually transferred from the closed lane to the open lane and the side mirror,indicating that the reduced lane-changing gap would make drivers pay more attention to confirm the lane-changing safety.The audio prompt warning could increase the visit duration on the side mirror in the perception stage and reduce the visit duration on the side mirror in the preparation stage.This demonstrated that the audio prompt could improve driver’s perceptual ability in the perception stage,thereby reducing the distraction from the side mirror during the preparation stage.(4)Based on the traffic conflicts between the lane-changing vehicle and the surrounding vehicles,a lane-changing risk assessment model was established to analyze the interaction risks and total risk of the merging process.The results showed that male drivers had a higher interaction risk with the lead vehicles in the closed and open lanes,thus they were more likely to be involved in rear-end collisions during lane changing.Traffic density was positive correlated with the total risk.What’s more,traffic density had various effects on the interaction risk.Specifically,the interaction risk between the lane-changing vehicle and the lead vehicle in the closed lane was negatively correlated with traffic density,while the interaction risk between the lane-changing vehicle and the lag vehicle in the open lane was positively correlated with traffic density.The reason for the former was the lower speed at high density condition reduced crash risks,while the latter was caused by the small lane-changing gaps which increased the merging risks.The analysis of the audio prompt showed that the too near or too far for releasing the lane-changing information were not conducive to traffic safety.The audio prompt at 250 m might stimulate the driver who took late merge to adopt aggressive driving behavior.However,when the audio prompt was set at1000 m upstream of work zone,the vehicle received the information might merge into the open lane at a faster speed,which increased the interaction risk with the lead vehicle in the open lane.Thus,the proper positions for setting audio prompt were advised to be500 m or 750 m.Additionally,this research also analyzed the influence of behavioral variables on the lane-changing risks,we found that the closer distance to the work zone,the larger S.D.of longitudinal velocity and the faster steering wheel velocity were always related with higher merging risks.(5)Based on the Cellular Automata simulation,the traffic efficiency under different audio prompt positions was tested,meanwhile,this paper also proposed a dynamic signal-based merge strategy with the consideration of queuing length.The effectiveness of the merge strategy was verified by analyzing traffic efficiency indicators.The results showed that the audio prompt at 250 m failed to improve the traffic efficiency since it was basically the same as that without audio prompt for all traffic efficiency indicators.As the audio prompt was set more in advance,the numbers of queuing vehicle in the closed lane and open lane gradually tended to balance.At the same time,the traffic delay on the road segment decreased and the traffic capacity at the bottleneck increased.Nevertheless,we still observed a large number of lane-changing behaviors in early merge scenarios,which definitely increased traffic hazards in work zone areas.Therefore,this research proposed a dynamic signal-based merge strategy to solve the traffic conflicts from the root causes.The results indicated that the proposed merge strategy could significantly reduce the frequency of lane changing,and guarantee greater traffic capacity and shorter queuing length under high traffic density conditions.Finally,the study suggested that audio prompt for early merge could be provided to improve lane-changing behavior at low traffic density condition,and the dynamic signal-based merge strategy should be applied at medium and high density conditions to ensure traffic safety at the expense of some traffic efficiency. |
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