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.

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.

Coordinated chaos control of urban expressway based on synchronization of complex networks

We investigate the problem of coordinated chaos control on an urban expressway based on pinning synchronization of complex networks. A node coupling model of an urban expressway based on complex networks has been established using the cell transmission model（CTM）. The pinning controller corresponding to multi-ramp coordinated controller was designed by using the delayed feedback control（DFC） method, whose objective is to realize periodical orbits from chaotic states. The concrete pinning control nodes corresponding to the subsystems of regulating the inflows from the on-ramps to the mainline were obtained and the parameters of the controller were optimized by using the stability theory of complex networks to ensure the network synchronization. The validity of the proposed coordinated chaos control method was proven via the simulation experiment. The results of the examples indicated that the order motion on urban expressway can be realized, the wide-moving traffic jam can be suppressed, and the operating efficiency is superior to that of the traditional control methods.

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.

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.

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.

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.

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.

Slope Protection with Vegetation of Baoji(Shaanxi)-Hanzhong(Shaanxi) Expressway

With expressway development and environment protection consciousness improving, slope protection technology with vegetation has drawn much more attention. From the perspective of ecology, Baoji-Hanzhong Expressway maximized slope protection technology with vegetation and formed attracting landscapes on basis of eco-protection. This research introduced the technology of Baoji-Hanzhong Expressway, and explored a low-cost and effective biological slopeprotection way, suitable for Baoji-Hanzhong Expressway, according to slope protection technologies, at home and abroad, with botany, water and soil conservation engineering, and architecture, which fixed and stabilized slopes, prevented rainfall scouring, and advanced slope protection development in China.

Construction of Cultural Landscapes along the Ya'an-Luguhu Expressway——Discussion about Techniques of Designing Highway Cultural Landscapes

The concept of cultural landscapes was introduced,and it was proposed that the construction of highway cultural landscapes should follow the principles of "protection first,secure,integrated,suitable for actual conditions,economic,natural and ecological".In this study,relevant theories were taken to analyze the design of cultural landscapes along the Ya'an-Luguhu Expressway in Sichuan Province.Natural conditions,profound cultures and historical resources in the study area were analyzed,and the construction of its cultural landscapes was further discussed from the perspectives of properly dividing landscape spaces,determining the orientation of cultural landscapes,refining regional cultures,choosing carriers of cultural landscapes,improving cultural value of important landscape nodes by using artistic settings,applying more local materials and so on.So that helpful references could be provided for the landscape design of other expressways,and the integration of cultural landscapes and highway landscape system could be realized.

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.

Review and perspective of expressway tunnels in Taiwan, China

Since the construction of the first expressway in the 1970s, the total length of expressways in Taiwan has increased to over 1 000 km, of which 40 km are aligned with tunnels. These twin-tube tunnels, which have two or three lanes in each tube, are characterized by large cross-sections. Due to the complicated topography and heterogeneous geological conditions of Taiwan, tunnel construction has encountered many difficulties. Thus, many advanced excavation methods were developed during tunnel construction. To satisfy the concurrent requirements of safety, economy and efficiency, new construction methods and techniques should be developed or introduced. Moreover, environmental protection and ecological conservation must be paid increasing attention to the goal of substantial development.

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.

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.

Automated extraction of expressway road surface from mobile laser scanning data

This paper presents a voxel-based region growing method for automatic road surface extraction from mobile laser scanning point clouds in an expressway environment.The proposed method has three major steps:constructing a voxel model;extracting the road surface points by employing the voxel-based segmentation algorithm;refining the road boundary using the curb-based segmentation algorithm.To evaluate the accuracy of the proposed method,the two-point cloud datasets of two typical test sites in an expressway environment consisting of flat and bumpy surfaces with a high slope were used.The proposed algorithm extracted the road surface successfully with high accuracy.There was an average recall of 99.5%,the precision was 96.3%,and the F1 score was 97.9%.From the extracted road surface,a framework for the estimation of road roughness was proposed.Good agreement was achieved when comparing the results of the road roughness map with the visual image,indicating the feasibility and effectiveness of the proposed framework.

Pre-evaluation on stability of proposed expressway embankment with existing geothermal regulation measures in permafrost regions

Embankment stability is the primary problem for the expressway construction in permafrost regions.The proposed Qinghai-Tibet Expressway(QTE)is planned to construct along the Qinghai-Tibet Project Corridor.Confronted with harsh environmental condition and intense heat exchange between earth and atmosphere,it is necessary to predict and evaluate the stability of the proposed QTE.In this study,the factors affecting the embankment stability are analyzed firstly.And then,a scheme for the stability evaluation of the embankment is established.Finally,the evaluation scheme is used for the pre-evaluation of the stability for the proposed QTE with different geothermal regulation measures(GRMs).The results indicate that the influencing factors include climatic environment,permafrost property,engineering condition and geological condition,and among them,engineering condition and permafrost property are the main influence factors for embankment stability.The stability of the proposed QTE varies greatly in the different geomorphological regions.The application effect and contribution to embankment stability of the existing GRMs are different,and using GRMs cannot completely overcome the influence of various factors on expressway stability.In the construction process,different GRMs should be adopted depending on the geomorphological environment where the embankment is located to ensure the embankment stability.

Expressway Traffic Flow Model Study Based on Different Traffic Rules

In this paper, two cellular automata traffic models are proposed to simulate the operation of an expressway. The results show that the flow rate and the average velocity are generally equal in the same density which is different among the lanes. The analysis of lane changing times and the velocity total deviation show some characteristics which are difficult to explain phase transitions under fundamental diagram theory. Therefore,the concept of lane changing probability is introduced, and it is concluded that the speed-limit rule can reduce the motivation of lane changing effectively.