沥青层隆起变形与松胀现象分析

分析了室内车辙试验试件、加速加载（ALF）车辙试验路芯样，以及沥青路面现场芯样的空隙率与高度变化，证实了在车辆荷载作用下沥青层的隆起变形与松胀现象，探讨了沥青层隆起部位松胀现象的产生机理与影响因素.以隆起系数表征隆起变形在总车辙变形中所占的比例，分析了隆起系数的影响因素与发展规律.通过对比分析，给出隆起系数的建议值范围为0-0.52，当道路宽度较窄时，隆起系数取上限；当道路宽度较大时，隆起系数取下限.

Evaluation of driving behavior based on massive vehicle trajectory data

Based on the driver surveillance video data and controller area network(CAN)data,the methods of studying commercial vehicles’driving behavior is relatively advanced.However,these methods have difficulty in covering private vehicles.Naturalistic driving studies have disadvantages of small sample size and high cost,one new driving behavior evaluation method using massive vehicle trajectory data is put forward.An automatic encoding machine is used to reduce the noise of raw data,and then driving dynamics and self-organizing mapping(SOM)classification are used to give thresholds or the judgement method of overspeed,rapid speed change,rapid turning and rapid lane changing.The proportion of different driving behaviors and typical dangerous driving behaviors is calculated,then the temporal and spatial distribution of drivers’driving behavior and the driving behavior characteristics on typical roads are analyzed.Driving behaviors on accident-prone road sections and normal road sections are compared.Results show that in Shenzhen,frequent lane changing and overspeed are the most common unsafe driving behaviors;16.1%drivers have relatively aggressive driving behavior;the proportion of dangerous driving behavior is higher outside the original economic special zone;dangerous driving behavior is highly correlated with traffic accident frequency.

A case study of performance-based pavement maintenance and rehabilitation needs assessment in Pennsylvania

This paper presents the theory,method,and application of performance-based pavement needs assessment at a state level,using the Pennsylvania Interstate System as an example.First,a general framework is presented for the pavement asset management and a general optimization model is established for the pavement maintenance and rehabilitation needs assessment.Also,the bundling of pavement segments for the project implementation is discussed.Using the examples of Statewide Transportation Improvement Plan and Long Range Transportation Plan for Pennsylvania Interstate System,the application of performance-based pavement needs assessment is demonstrated.It is shown that unconstrained analysis can help decision-makers investigate the real maintenance and rehabilitation needs;financially-constrained analysis can help decision-makers select projects for implementation and examine the corresponding future pavement conditions.Trade-off analysis can help decision-makers investigate the outcomes of different investment levels on pavement maintenance and rehabilitation and make the final decision on the investment level.The proposed case study provides a good example of performance-based pavement needs assessment for developing countries.

Big data assessment on the operating characteristics of on-line taxis and thoughts on relevant policies

A double-dimensional big data assessment method on the characteristics of on-line taxi traffic operation is proposed to provide a scientific basis for carrying out the taxi industry reform and standardizing the on-line taxi hailing management work. Taking Shenzhen as an example, multi- source data such as on-line taxi license plate data, plate identification data and taxi （including on-line taxis） operation data are combined with the results of the stated preference （SP） survey on taxi operating characteristics to assess the overall operation characteristics of on-line taxis. The results show that the current on-line taxis in Shenzhen can be divided into three categories, that is, full-time on-line taxis, non- active on-line taxis and part-time on-line taxis, accounting for 4%, 55%, and 41%, respectively, of the total quantity. In terms of the characteristics of space-time operations, full-time on-line taxis have similar operating characteristics as those of traditional taxis; the operation of non-active on-line taxis and part-time on-line taxis coincides with commuting requirements during morning and evening peak hours. However, part-time on-line taxis operate for a much longer time period at night. Due to the convenient hailing and favorable price, on-line taxis have a significant impact on trip modes of citizens; and the substitution eflbct of on-line taxis on traditional buses and cruising taxis is obvious. It is beneficial for helping the government departments to objectively understand the development law of the on-line taxi industry and providing decision reference for the formulation of relevant management policies during the critical development stage of on-line taxi industry.

Updating method of a high-speed maglev guideway model based on wavelet transform

The structure of a high-speed maglev guideway is taken as the research object.With the aim of identifying the inconsistency of modal parameters between the simulation model and the actual model,and based on the 600 km/h high-speed maglev vehicle and the high-speed maglev test line,the arrangement of sensors and the vibration acceleration data collection of the 12.384 m concrete guideway were conducted.The modal parameters were identified from the guideway response signal using wavelet transform,after which the wavelet ridge was extracted by using the maximum slope method.Next,the vibration modes and frequency parameters of the interaction vibration characteristics of the high-speed maglev guideway and 600 km/h maglev vehicle were analyzed.The updating objective function for the finite element model of the guideway was established,and the initial guideway finite element model was modified and updated by repeatedly iterating the parameters.In doing so,the model structure of the high-speed maglev guideway was obtained,which is consistent with the actual structure.The accuracy of the updated guideway model in the calculation of the dynamic response was verified by combining this with the vehicle-guideway coupling dynamic model of the high-speed maglev system with 18 degrees of freedom.The research results reveal that the model update method based on the wavelet transform and the maximum slope method has the characteristics of high accuracy and fast recognition speed.This can effectively obtain an accurate guideway model that ensures the correctness of the vehicle-guideway coupling dynamic analysis and calculation while meeting the parameters of the measured structure model.This method is also suitable for updating other structural models of high-speed maglev systems.

Analysis of bicyclist-vehicle crash at intersection area considering behavior prior to crash:A random parameter ordinal probit approach

In order to analyze the risky factors that affect vehicle-cyclist crash injury severity at the intersection area,especially the factors relating to the road users behaviors,an empirical study was conducted by collecting accident records from 2011 to 2015 from the General Estimates System.After preliminary screening,the variables were classified into 5 main categories including cyclists characteristic and behavior,drivers characteristic and behavior,vehicle characteristic,intersection condition,and time.The random parameter ordinal probit(RPOP)was used to study the significant influencing factors and corresponding heterogeneity.The results show that failing to obey traffic signals,failing to yield to right-of-way,dash and drinking before cycling can increase the injury severity for cyclists,and the corresponding fatal injury likelihoods increase by 53.2%,40.0%,86.3%,and 211.5%,respectively.Moreover,drivers inattention,speeding,going straight and left turning increase the risk of crashing for cyclists.The corresponding fatal injury likelihoods increase by 134.5%,186.5%,69.3%,and 22.7%,respectively.Other indicators such as age,gender,vehicle type,traffic signal and intersection type can also affect injury severity.

Prediction of a maximum pull-out load of anchor bolts using an optimal combination model

The mixed model of improved exponential and power function and unequal interval gray GM(1,1)model have poor accuracy in predicting the maximum pull-out load of anchor bolts.An optimal combination model was derived using the optimally weighted combination theory and the minimum sum of logarithmic squared errors as the objective function.Two typical anchor bolt pull-out engineering cases were selected to compare the performance of the proposed model with those of existing ones.Results showed that the optimal combination model was suitable not only for the slow P-s curve but also for the steep P-s curve.Its accuracy and stable reliability,as well as its prediction capability classification,were better than those of the other prediction models.Therefore,the optimal combination model is an effective processing method for predicting the maximum pull-out load of anchor bolts according to measured data.