Identification and characteristics analysis of bottlenecks on urban expressways based on floating car data

Identifying bottlenecks and analyzing their characteristics are important tasks to city traffic management authorities.Although the speed difference was proposed for the bottleneck identification in the existing research,the use of a secondary indicator has not been fully discussed.This paper strived to develop a method to identify the bottleneck on expressways by using the massive floating car data(FCD)in Beijing.First,the speed characteristics of bottlenecks on expressway were analyzed based on the speed contour map.The results indicated that there was a significant difference between speeds on the bottleneck and downstream links when a bottleneck was observed.The speed difference could indeed be used as the primary indicator to identify the bottleneck.However,it was also shown that a sufficiently large speed difference does not necessitate an activation of a bottleneck.The speed-at-capacity was then used as the secondary indicator to distinguish the real bottleneck from the non-bottleneck speed difference.Second,a practical method for identifying the bottleneck on expressways was developed based on the speed difference and the speed-at-capacity.Finally,the method was applied to identifying the bottlenecks of the 3rd Outer Ring Expressway in Beijing.The duration,affected distance,delay and cause were used to evaluate and analyze the bottlenecks.

Effect of the W-beam central guardrails on wind-blown sand deposition on desert expressways in sandy regions

Many desert expressways are affected by the deposition of the wind-blown sand,which might block the movement of vehicles or cause accidents.W-beam central guardrails,which are used to improve the safety of desert expressways,are thought to influence the deposition of the wind-blown sand,but this has yet not to be studied adequately.To address this issue,we conducted a wind tunnel test to simulate and explore how the W-beam central guardrails affect the airflow,the wind-blown sand flux and the deposition of the wind-blown sand on desert expressways in sandy regions.The subgrade model is 3.5 cm high and 80.0 cm wide,with a bank slope ratio of 1:3.The W-beam central guardrails model is 3.7 cm high,which included a 1.4-cm-high W-beam and a 2.3-cm-high stand column.The wind velocity was measured by using pitot-static tubes placed at nine different heights(1,2,3,5,7,10,15,30 and 50 cm)above the floor of the chamber.The vertical distribution of the wind-blown sand flux in the wind tunnel was measured by using the sand sampler,which was sectioned into 20 intervals.In addition,we measured the wind-blown sand flux in the field at K50 of the Bachu-Shache desert expressway in the Taklimakan Desert on 11 May 2016,by using a customized 78-cm-high gradient sand sampler for the sand flux structure test.Obstruction by the subgrade leads to the formation of two weak wind zones located at the foot of the windward slope and at the leeward slope of the subgrade,and the wind velocity on the leeward side weakens significantly.The W-beam central guardrails decrease the leeward wind velocity,whereas the velocity increases through the bottom gaps and over the top of the W-beam central guardrails.The vertical distribution of the wind-blown sand flux measured by wind tunnel follows neither a power-law nor an exponential function when affected by either the subgrade or the W-beam central guardrails.At 0.0H and 0.5H(where H=3.5 cm,which is the height of the subgrade),the sand transport is less at the 3 cm height from the subgrade surface than at the 1 and 5 cm heights as a result of obstruction by the W-beam central guardrails,and the maximum sand transportation occurs at the 5 cm height affected by the subgrade surface.The average saltation height in the presence of the W-beam central guardrails is greater than the subgrade height.The field test shows that the sand deposits on the overtaking lane leeward of the W-beam central guardrails and that the thickness of the deposited sand is determined by the difference in the sand mass transported between the inlet and outlet points,which is consistent with the position of the minimum wind velocity in the wind tunnel test.The results of this study could help us to understand the hazards of the wind-blown sand onto subgrade with the W-beam central guardrails.

Design Strategy of New and Reconstructed Interchanges on Expressways

China's urban development is very fast,and the continuous improvement of the national economic level in recent years has also prompted most families to have their own scooters.In this situation,the increase and transformation of road traffic has been a necessary work for the development of various regions.This paper starts with the basic reasons for the design of new and improved interchanges,and expounds the specific design type division and main influencing factors.Finally,the paper puts forward the design strategy of newly added and reconstructed interactive interchanges with high feasibility,hoping to provide reasonable reference for relevant road traffic engineering optimization.

Reinforcement Technology for Soft Soil Roadbed in the Widened Section of Expressway Expansion

This article examines the soft soil roadbed reinforcement technology for widened sections of highways in a specific project.It provides an overview of the project,the principles of soft soil roadbed reinforcement technology for wide sections,and its practical application.The analysis aims to offer guidance on applying soft soil roadbed wide section reinforcement technology and enhancing the overall quality of similar projects.

Analysis of Bridge Inspection Technology for Highway Reconstruction and Expansion

This article focuses on bridge testing technologies in highway construction and expansion projects.It provides an overview of the inspection process for bridges in highway reconstruction and expansion projects,the main inspections,and strategies for improving the quality of inspections.Relevant units should conduct bridge inspections using appearance inspections,special inspections,and bearing capacity assessments in highway reconstruction and expansion projects.To effectively improve testing quality,relevant units should also focus on establishing and improving testing standards,strengthening material testing,and improving the overall quality of the testing personnel.This research aims to enhance the quality of highway reconstruction and expansion projects by supporting the sensible application of bridge inspection technology.

A GIS-Based Framework for Real-Time Debris-Flow Hazard Assessment for Expressways in Korea

Debris flows caused by heavy rainfall in mountain areas near expressways lead to severe social and economic losses and sometimes result in casualties.Therefore, the development of a real-time system for debris-flow hazard assessment is necessary to provide preliminary information for rapid decision making about evacuations or restoration measures, as well as to prevent secondary disasters caused by debris flows. Recently,various map-based approaches have been proposed using multi-attribute criteria and assessment methods for debrisflow susceptibilities. For the macrozonation of debris-flow hazard at a national scale, a simplified method such as the Korea Expressway Corporation(KEC) debris-flow hazard assessment method can be applied for systematic analysis based on geographic information systems(GIS) and monitoring networks. In this study, a GIS-based framework of real-time debris-flow hazard assessment for expressway sections is proposed based on the KEC debris-flow hazard assessment method. First, the KEC-based method was standardized in a systematic fashion using Arc GIS,enabling the objective and quantitative acquisition of various attribute datasets. The quantification of rainfall criteria also was considered. A safety management system for debris-flow hazard was developed based on the GIS platform. Finally, the method was applied and verified on three expressway sections in Korea. The grading standard for each individual influencing attribute was subsequently modified to more accurately assess the debris-flow hazards.

Heavy metals in road-deposited sediment and runoff in urban and intercity expressways

Road-deposited sediments(RDS)accumulated on road surfaces are an important environmental medium that often provides transport for heavy metals.In order to understand the characteristics of heavy metals in RDS,we investigated the size distribution and heavy metal(i.e.Cd,Cr,Cu,Ni,Pb and Zn)concentrations in RDS and road runoff in typical expressways of suburban and rural area in China.The results demonstrated that RDS particles from all impervious expressway surfaces were predominantly coarse particles(>250μm,58.4%±3.8%)and the RDS on all expressways contained more heavy metals than background soils.Furthermore,the concentrations of Cd,Cr,Cu,Ni,Pb and Zn increased with traffic volume,suggesting that these heavy metals are mainly derived from traffic activities.Moreover,it is found that although heavy metals were concentrated in fine grain fractions,the total loading is highest for the coarsest particles due to their large mass percentage.Additionally,it reveals that the heavy metal concentrations in road runoff of suburban expressway are higher than that in urban expressway.Our findings enhance the understanding of expressway pollution,and imply that for controlling runoff pollution from RDS,transportation agencies should be concerned with both fine and coarse particles and take cleaning methods into account.

Integrating predictive modeling techniques with geospatial data for landslide susceptibility assessment in northern Pakistan

The eastern road section of the ChinaPakistan Economic Corridor(CPEC)traverses the challenging terrain of northern Pakistan,where frequent landslides pose a significant threat to socioeconomic development and infrastructure.However,the insufficient data on landslide hazards presents a substantial challenge to practical mitigation efforts.Therefore,we conducted an extensive study to gain insight into landslide assessment along the Mansehra-Muzaffarabad-Mirpur and Mangla(MMMM)Expressway.This study involved preparing a landslide inventory,analyzing landslide causative factors,and developing landslide susceptibility models(LSMs)using published data,remote sensing interpretations,field excursions and integrated predictive techniques.We first used Pearson's correlation coefficient(PCC),variable importance factors(VIF),and information gain ratio(IGR)to evaluate multicollinearity among the selected landslide causative factors(LCFs).Then,the topographic roughness index(TRI)with VIF>5 and PCC>0.7 was considered a redundant factor and thus removed before the data modeling.Finally,we adopted multiple machine-learning methods to analyze landslide susceptibility.The results indicate that the landslide inventory contains 1,776 events,of which 674 were classified based on geometrical and lithological configurations.The IGR results show that the rainfall,lithology,PGA,drainage density,slope,and distance to fault are the most effective LCFs.The AUC values for random forest(RF)(0.901),extreme gradient boosting(XGBoost)(0.884),and K-nearest neighbor(KNN)(0.872)remained higher than evidential belief function(EBF)(0.833),weight of evidence(WoE)(0.820),and certainty factor(CF)(0.810),respectively.The RF model outperformed all other models in terms of prediction.However,these models are accurate but newer in the area;thus,susceptible zones were verified with comprehensive field investigations.The northern and central regions accounted for the high and very high susceptibility classes in the final landslide susceptibility mapping(LSM)compared to the southern areas.

Analysis of Highway Subgrade Slope Protection and Support Technologies

As an important transportation hub in China,the traffic volume and driving speed are important aspects of expressways.Therefore,the protection requirements for roadbed side slopes are higher,and it is necessary to resist rainwater erosion and other damages by protecting the side slopes.Therefore,it is necessary to adopt effective technical means of subgrade protection and support.This paper mainly summarizes the characteristics of highway subgrade slope protection construction and slope protection and support technologies.

Design Strategies of Expressway Routes and Interchanges

Road traffic conditions can have an important impact on the economic development of various regions.Under the background of rapid social and economic development,more and more expressway construction projects are initiated in various regions,including both new expressways and expansion of old expressways,and interchange design plays an important role.Scientific and reasonable interchange design can not only realize energy saving and low carbon footprint,but also be people-oriented and promote regional economic development.Therefore,this paper mainly analyzes the highway route and its interchange design strategy for reference.

Study on Optimization of Design Parameters for Precast Pipe Pile Treatment of Soft Soil Subgrade on the Jianghan Plain

The soft soil in the Jianghan Plain is characterized by a high water content, liquid limit, sensitivity, porosity ratio, and organic matter content and low strength and is commonly known as “five highs and one low” soft soil. Thus, the construction of expressways in this area is likely to cause subgrade settlement. The manuscript investigated the influence of the design parameters of precast pipe piles on the soft ground treatment in the Jianghan Plain based on the case of the soft soil subgrade project of the Xiaogan south section of the Wuhan city ring expressway, China. Midas GTS NX 2019 finite element software was used to analyse the settlement pattern of the subgrade under the variations in pile length, pile spacing and pile diameter. The results show that precast pipe piles are effective in reducing the settlement of soft soil subgrades with a high compressibility and water content;the soft foundation settlement decreases with increasing pile length and pile diameter and decreasing pile spacing. As the pile tip is embedded in the bearing stratum, the settlement of the soft foundation is greatly affected by the variations in pile length and pile spacing while slightly influenced by the variation in pile diameter;in combination with the curve fitting obtained from the real-time monitoring data, the analysis concludes that the soft foundation treatment plan with a pile length of 15 m, pile spacing of 1.2 m to 1.5 m and pile diameter of 0.6 m can better contain the soft soil subgrade settlement in this section.

Research on Traffic Safety at Tunnel Entrance and Exit

Highway tunnel entrances have a high rate of expressway traffic accidents.In this paper,the reasons for the high incidence of traffic accidents at highway tunnel entrances are analyzed in detail,and corresponding solutions are proposed,hoping to provide some reference to relevant parties.

Reliability Design for Longitudinal Slope Length of Expressway

The significance and the strategies of applying the reliability design method of longitudinal slope length in expressway engineering were explored in this study.The objective is to offer insights that can be beneficial for designing longitudinal slope lengths in contemporary expressway projects,with a focus on enhancing their reliability and safety.

Expressway Route and Interchange Design

With the rapid development of the socio-economy and the growing demand for transportation,highways have become an indispensable and important part of the modern transportation network.The design of highway routes and interchanges is a key link in highway construction,which directly affects the efficiency,safety,and traffic smoothness of highways.Based on this,this article analyzes in detail the highway route design and the design of two common interchanges,in order to improve the highway route design and the quality and efficiency of highway construction.

Ecological Design of Expressway Based on the Perspective of Landscape Ecology

The construction and operation of expressways will also bring a series of environmental and ecological problems,such as land use conflicts,ecological damage,environmental pollution,etc.In order to solve such problems,it is necessary to strengthen the application of landscape ecology.From the perspective of landscape ecology,this paper first introduces the impact of expressways on the ecological environment,and then analyzes the principles of expressway ecological landscape design.Landscaping,ecological environment,customer satisfaction,and other aspects have all performed well,with an optimization rate of over 90%.Future expressway design can strengthen the application of landscape ecology.

Analysis and Research on Interchange and Expansion options of Expressway

China's road network consists of numerous older expressways experiencing high traffic volumes and severe congestion,necessitating urgent reconstruction and expansion efforts.This study discusses the reconstruction and expansion project of the Yinkun Expressway's Chongqing High-tech Zone to Rongchang District section,with a detailed exploration of the entire design process.Through a comprehensive analysis,the strengths and weaknesses of different plans are examined,so as to determine the optimal plan.The design chosen saves costs while effectively addressing traffic demands.Additionally,the study summarizes the valuable design insights gained from this interchange transformation,aiming to provide valuable reference for similar interchange projects in the future.

Decision model and algorithm for traffic rescue resource dispatching on expressway

In order to solve the problems of potential incident rescue on expressway networks, the opportunity cost-based method is used to establish a resource dispatch decision model. The model aims to dispatch the rescue resources from the regional road networks and to obtain the location of the rescue depots and the numbers of service vehicles assigned for the potential incidents. Due to the computational complexity of the decision model, a scene decomposition algorithm is proposed. The algorithm decomposes the dispatch problem from various kinds of resources to a single resource, and determines the original scene of rescue resources based on the rescue requirements and the resource matrix. Finally, a convenient optimal dispatch scheme is obtained by decomposing each original scene and simplifying the objective function. To illustrate the application of the decision model and the algorithm, a case of the expressway network is studied on areas around Nanjing city in China and the results show that the model used and the algorithm proposed are appropriate.

Analysis of Heavy Metal Content in Food Crops Planted Along the Shaanxi Inner Mongolia Expressway

To understand the effect of the running of Shaanxi Inner Mongolia Expressway on food crops planted along the sides, we determined the heavy metal contents(Zn, Pb, Cu and Cb) in the digestion solutions of the root, stem and leaf from rice and corn. The results showed that highway promoted the accumulation of heavy metal elements in corn and rice. Compared with the CKs(crops produced where no highway extend), contents of heavy metal elements in two crops tested from two sampling sites were both over standard. This indicates that food crops planted within 100 m away from the highway are been polluted by heavy metals, which is directly related with the running of Shaanxi Inner Mongolia Expressway. Based on this, the areas within 100 m away from the highway are not suggested to cultivate food crops.

Expressway traffic flow prediction using chaos cloud particle swarm algorithm and PPPR model

Aiming at the real-time fluctuation and nonlinear characteristics of the expressway short-term traffic flow forecasting the parameter projection pursuit regression PPPR model is applied to forecast the expressway traffic flow where the orthogonal Hermite polynomial is used to fit the ridge functions and the least square method is employed to determine the polynomial weight coefficient c.In order to efficiently optimize the projection direction a and the number M of ridge functions of the PPPR model the chaos cloud particle swarm optimization CCPSO algorithm is applied to optimize the parameters. The CCPSO-PPPR hybrid optimization model for expressway short-term traffic flow forecasting is established in which the CCPSO algorithm is used to optimize the optimal projection direction a in the inner layer while the number M of ridge functions is optimized in the outer layer.Traffic volume weather factors and travel date of the previous several time intervals of the road section are taken as the input influencing factors. Example forecasting and model comparison results indicate that the proposed model can obtain a better forecasting effect and its absolute error is controlled within [-6,6] which can meet the application requirements of expressway traffic flow forecasting.

Study of macroscopic fundamental diagram on Shanghai urban expressway network in China

The macroscopic fundamental diagram（ MFD） is studied to obtain the aggregate behavior of traffic in cities. This paper investigates the existence and the characteristics of different types of daily MFD for the Shanghai urban expressway network. The existence of MFD in the Shanghai urban expressway network is proved based on two weeks＇ data.Moreover, the hysteresis phenomena is present in most days and the network exhibits different hysteresis loops under different traffic situations. The relationship between the hysteresis phenomena and the inhomogeneity of traffic distribution is verified. The MFDs in the years of 2009 and 2012 are compared. The hysteresis loop still exists in 2012, which further verifies the existence of the hysteresis phenomenon. The direct relationship between the length of the hysteresis loop（ ΔO） and the congestion is proved based on sufficient data. The width of the hysteresis loop, i. e., the drop in network flow（ ΔQ） has no relationship with the congestion, and it varies from day to day under different traffic situations.