Abstract

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Title:: Reasonable speed difference on uphill section of mountainous freeways

Author(s):: -; WANG Xianliang1，2, ZHANG Xiaodong1, XU Jinliang1, JIA Xingli1

Keywords:: traffic engineering; reasonable speed difference; regression analysis; mountainous freeway; traffic efficiency

Abstract:: Aimed to study the traffic efficiency and safety enabled by the speed difference between trucks and regular traffic flow on the uphill section of a mountainous freeway. A field experiment was carried out in Xihan (Xian to Hanzhong) Freeway from K1185+120 to K1185+820. Traffic data consisting of location, speed, headway time, interval and vehicle type, which were collected on a timely basis using AxleLight RLU11. Platoons were chosen according to vehicular headway, and then, the database comprising speed difference and average speed were built. After the normal distribution test, the regression model was established with the speed difference as the independent variable, and the average speed as the dependent variable through SPSS. The threshold value of speed difference influencing traffic efficiency was further determined, compared to the platoon without trucks. The results show that mixed driving with trucks has a considerable influence on traffic efficiency. The average speed of a platoon with trucks shows a significant decrease, about approximately 13.6% compared to a platoon without trucks. Speed reduction has a quadratic correlation with the dispersion of average speed, traffic efficiency can be well maintained by limiting the allowable speed reduction to approximately 21 km/h. 5 tabs, 7 figs, 18 refs.