Speed Zone Division And Speed Transition Zone Setting Research

Speeding is a leading cause of traffic accidents according to related statistics in China , which threats road safety.The total number of road traffic injuries and fatalities can not be able to forecast exactly .Up till now ,government has undertook many measures to balance the interests of mobility and safety. Successful speed management is an important component of roadway management,while unreasonable speed limits may play an verse.At present,China road traffic satety law establishes the maximum speed limit at which vehicles are permitted to travel on freeway and urban roadway. However, it does not consider factors such as vehicles'features, roadside interference ,roadway factors.What's more, setting flow of speed limit is not reasonable and uniform.The paper introduces a western transportation construction projects called speed management and speed control which took freeway and first and secondary roadways as research subjects. Traffic volulmes,road aligment and passenger car were collected from Xinjiang,Yunnan,Sichuan,Jiangxi,Shaanxi provinces. Statistics and mathmatics modeling process and linear regression are applied to speed zones and transitions zones setting process.The paper includes speed difference analysis, speed zones division identify , determination of length of speed zones and transition zones .Uniform speed limit is a popular and widely used method, which mainly depend on design speed . All design process is easy and convienet.Single speed limit are not inconsistant with raodway atcual condition which leads to low compliance.The paper first figures out concepts of speed zone and speed transition zone.It develops methods and procedures on different roadway respectively.The subjects are divided into three types:1)Plain Expressway; 2)Mountainous Highway; 3)First and Secondary roads.The paper first analyzes the impact facts of speed zone and proposed a speed limit schedule based on speed difference threshold. Targent method are used to quantify various factors ,then cluster analysis are used according to adjacent sections of coefficient of variation .Clustering results is the final division .Speed difference probability concept was introduced to identify highway and secondary road for updating speed zone and transition zone setting. Typical road scences which leads to 10km /h, 15km /h, 20km/h, 30km/h,40km/h speed differences under VISSIM software environment . Car speed stability is taken as an indicator to determine when to update speed zone. Speed difference of adjacent section under 10km/h, 15km/h, 20km/h, 40km/h under conditions of the adjacent section of the speed and speed stability of the trend.The simulation results shows that if speed difference is greater than the adjacent section of 10km / h in the case, speed limit zone needs to be updated.If the speed difference is greater than 20km / h transition section should be inserted between speed zones.Data from highway speed zonse on the plains freeway were analysized. Only in the interchange area and road toll stations need to update speed zone. Speed limit is generally between 40km / h ~ 80km / h, speed transition zone should be insert.Speed limit value should consider radis,length of slope,traffic volumes and traffic composition. Coorelation analysis with SPSS software is used to determine speed zone updated at small radius sections,long slope and long tunnel. Because of its interference factors are more complex for secondary roads, advisory speed signs are proposed for small radius horizontal curve, roadway through village, long downhill.Road speed limit should 10km / h ~ 30km / h lower than arterial.Driving safety and short-term memory includes to consider the minimum length of speed limit zone. 42 subjects are selected to take part in indoor laboratory. Exponential model for short-term memory are fitting using memory data after 5s, 10s, 15s, 20s, 25s, 35s, 45s. Minimum length of speed limit zones should consists of a distance of 40 seconds for a safety driving and a traffic signs in advance when speed limit is lower than 80km/h.While is consists of a 60 seconds distrance , when speed limit is higher than 80km/h. The actual experimental data and simulor are applied to caculate the length of transition zones. Considering traffic sign legibility distance, safety distance and difference between adjacent speed areas to calculate a reasonable length of transition zone.This paper results are based on actual data and complete the proposal for setting speed limit for highway and rural two lane.Through software simulation, the speed zone update threshold and speed transition zone threshold are provided for highway speed management.