Effects of changing highway design speed

In an effort to increase the operational efficiency of highways, South Korea has been increasing its design speed recently. However, the use of higher design speed will also increase construction costs. Moreover, increasing the design speed is expected to have an impact on safety. Hence, there is a strong need to demonstrate that the benefits outweigh the cost of having a higher design speed. This study surveyed a sample of design engineers to determine their awareness of the consequences of increasing design speed and their assessment of the right design speed for an actual rural arterial road. In addition to the survey, a case study of three recently upgraded highways was conducted to determine the changes in traffic volumes, speeds, travel times and accidents. The construction costs associated with the upgrades were also reported. Copyright © 2011 John Wiley & Sons, Ltd.     

Accident cost saving and highway attributes

Two semi-logarithmic regression models are developed to estimate accident rates and accident costs, respectively, for rural non-interstate highways in the state of Iowa. Data on 21,224 accidents occurring between 1989 and 1991 on 17,767 road segments are used in the analysis. Seven road attributes of these road segments are included as predictor variables. Applying the resulting regression models to a rather typical highway upgrade situation, the present value of the accident cost saving is computed. The sensitivity of the estimated cost saving to values for fatal, personal injury, and property damage only accidents is tested.Because factors other than road characteristics greatly influence accident costs, the models developed in this research explain a limited amount of the variance in these costs among road segments. Results of the analysis indicate that the most important attribute associated with accident costs is average daily traffic per lane, followed by conditions requiring passing restrictions and the sharpness of curves. Varying the values for the three categories of accidents shows that results are far more sensitive to the value of personal injuries than fatalities. The feasibility of using predictive models of accident costs in benefit-cost analyses of highway investments is demonstrated.     

农村公路的建设与设计

通过农村公路建设原则,提出了农村公路网建设要重实用、重排水、重防护的设计要点。     

Jointly optimizing cost, service, and environmental performance in demand-responsive transit scheduling

In certain fleet systems, the environmental impacts of operation are, to some extent, a controllable function of vehicle routing and scheduling decisions. However, little prior work has considered environmental impacts in fleet vehicle routing and scheduling optimization, in particular, where the impacts were assessed systematically utilizing life-cycle impact assessment methodologies such as those described by the Society of Environmental Chemistry and Toxicology. Here a methodology is presented for the joint optimization of cost, service, and life-cycle environmental consequences in vehicle routing and scheduling, which we develop for a demand-responsive (paratransit or dial-a-ride) transit system. We demonstrate through simulation that, as a result of our methodology, it is possible to reduce environmental impacts substantially, while increasing operating costs and service delays only slightly.     

Relationships between highway capacity and induced vehicle travel

The theory of induced travel demand asserts that increases in highway capacity will induce additional growth in traffic. This can occur through a variety of behavioral mechanisms including mode shifts, route shifts, redistribution of trips, generation of new trips, and long run land use changes that create new trips and longer trips. The objective of this paper is to statistically test whether this effect exists and to empirically derive elasticity relationships between lane miles of road capacity and vehicle miles of travel (VMT). An analysis of US data on lane mileage and VMT by state is conducted. The data are disaggregated by road type (interstates, arterials, and collectors) as well as by urban and rural classifications. Various econometric specifications are tested using a fixed effect cross-sectional time series model and a set of equations by road type (using Zellner’s seemingly unrelated regression). Lane miles are found to generally have a statistically significant relationship with VMT of about 0.3–0.6 in the short run and between 0.7 and 1.0 in the long run. Elasticities are larger for models with more specific road types. A distributed lag model suggests a reasonable long-term lag structure. About 25% of VMT growth is estimated to be due to lane mile additions assuming historical rates of growth in road capacity. The results strongly support the hypothesis that added lane mileage can induce significant additional travel.     

A highway capacity function in Korea: Measurement and calibration

Capacity functions are important in the model that accounts for the user's route choice behavior based on the traveller's perception of the travel time. This is because a capacity function represents the relationship between the traffic volume and the travel time on the link. The capacity function developed by the U.S. Bureau of Public Roads (BPR) has been used in many countries, including Korea, without much effort to calibrate the parameters for its own transportation environment. Countries other than the United States, however, have distinctive demographic, economic, cultural, and behavioral characteristics; and they might need unique capacity functions for their own environments. Thus, it is important for Korea to have its own capacity function that can appropriately represent the Korea highway environment. Any attempt to model the Korean highway system without using a suitable capacity function might result in inappropriate solutions, because most modeling activities are crucially based on link travel time, and it is the capacity function that furnishes those link travel time. A link capacity function for Korea is calibrated based on a BPR type formula utilizing an alternative method. The alternative method is developed in a bilevel programming framework that uses link volume counts instead of link flow and travel time data. Detailed calibration results are reported.     

Traffic engineering and the new German highway capacity manual

Traffic engineering in Germany has a long tradition. The standards for practical application, however, are distributed among a variety of guidelines. These, in many cases, are not up to date. Therefore, in practice, more recent research results are applied by traffic authorities and consultants. To improve this practical application on a more sophisticated background, a manual for traffic quality and capacity on streets and highways is intended to be prepared. A first draft has been worked out by a university institute and is to be published in 1994. This article presents the background for the chapter on highway sections and motorway interchanges for signalized and unsignalized intersections. Pedestrian and public transit facilities are mentioned as well. Special attention is drawn to the most recent research results which are included in the manual. These are delays at intersections under nonstationary conditions, including queue length and distributions (e.g. 95-percentile queue length). For motorways, the lack of a general speed limit in Germany has important impacts on determining measures of effectiveness.     

How the environmental impact affects the design of logistics networks based on cost minimization

The degree of centralization of the logistics network is one of the important strategic decisions to take. This issue has often been studied but mainly from a cost minimization focus. This research studies the influence of incorporating the environmental impact in logistics network design models, comparing the results with those obtained considering cost minimization only. A fuzzy biobjective optimization model is used to carry out a number of experiments. By weighting the relative importance of the two objectives, the differences with respect to the base cost minimization solution can be ascertained. Our results show that in general more material is moved through warehouses when the environmental impact is considered and more decentralized facilities are opened.     

Morphological approach to metropolitan highway systems analysis,planning, and policy design

Morphology is the subject matter of study in physical and biological sciences. A few attempts have been made to apply the biologists’ and paleontologists’ morphological study model known as allometry to social sciences fields and urbanization dynamics. However in social and sociocultural situations all forms are changeable by volition and policy, as opposed to being the result of fixed information which is stored in the genes. In studying metropolitan areas it is advantageous to regard the allometric relations as merely morphological relations indicating norms by which the components of the system change in relation to the change of the whole system. The morphological analysis approach for a metropolitan highway system has been formulated by utilizing relations defined in the Tri‐State metropolitan area (Connecticut, New Jersey, and New York). The study demonstrates that this approach is suitable for highway network planning and comprehensive policy design.     

Comparisons of the environmental footprint of heavy vehicles in the UK and Switzerland

The European Union project Eureka Logchain Footprint is an ongoing project to identify road and rail vehicles by means of their environmental footprint as characterised by dynamic load, noise, ground borne vibrations and gaseous emissions induced by the vehicle. Part of the project involves the installation of road and rail footprint monitoring stations throughout Europe. This paper presents results of the road stations in Switzerland and the UK. Individual vehicle data from weigh-in-motion and noise are compared. The results indicate that a significant number of vehicles surpass the limits set in both countries. It was shown that the UK sites are generating higher noise levels than their Swiss counterparts; in part due to the much coarser aggregate embedded in the running course of the pavement employed in the UK. Such data can be used to create an incentive for vehicle types with a low footprint and a penalty for vehicles with a large footprint.     

The relationship among highway geometrics,traffic-related elements and motor-vehicle accident frequencies

This research provides a demonstration of a statistical model of accident frequency that can eventually be used as part of a proactive program to allocate safety-related highway improvement funds. Negative binomial regressions of annual accident frequency on sections of principal arterials in Washington State were estimated using data from two years (1992 and 1993). In all, 31306 observations were used in model estimation (annual accident frequencies on specific sections of highway). Our estimation results isolated the effects of various highway geometric and traffic characteristics on annual accident frequency. Subsequent elasticity computations identified the relative importance of the variables included in our specifications. The findings show that the negative binomial regression used in this paper is a powerful predictive tool and one that should be increasingly applied in future accident frequency studies.     

Superpave设计方法在榆(林)靖(边)高速公路中的应用

针对榆靖沙漠高速公路气候特点,采用Su-perpave设计方法对沥青混合料进行设计,对试验路压实度、构造深度、路面弯沉、裂缝等质量控制指标进行测试,分析结果表明Superpave沥青混凝土路面具有优良的路用性能,所采用的材料组成设计方法在沙漠地区地区具有广泛的应用前景。     

公路网规划环境影响评价内容、程序和方法体系研究

在总结研究目前国内已有公路网规划环境影响评价工作的基础上,根据规划环境评价的目标要求和公路网规划的实际,提出了包括内容、程序和方法等的公路网规划环境影响评价体系,提高现有公路网规划环境评价能力和未来公路网规划环境评价质量。     

特长公路隧道通风设计若干问题与对策

目前,我国在特长公路隧道的通风设计中,在隧道自然风阻力计算、根据稀释烟雾计算隧道需风量、送排式通风系统中“不应有短道回流”和通风斜井倾角选用等方面存在一定的问题。文章在对问题进行分析论证的基础上提出:(1)隧道自然风阻力应由自然风等效压差确定,在缺少工程实地观测资料的情况下,假定隧道自然风阻力为常量,并在10~30 Pa之间取值;(2)依据稀释烟雾计算隧道需风量时,在公式中应引入烟雾的质量浓度或烟雾的体积浓度,并用其替代公式中的一般烟雾浓度;(3)竖井送排式通风系统中宜变短道顺流为有控制的回流;(4)隧道通风斜井的倾角不要受矿山常用的斜井倾角的限制,应视隧道的具体工程条件灵活取用。     

论高速公路边坡水土保持植物防护设计

通过对高速公路边坡水土保持的研究,主要论述边坡水土保持植物防护设计的应用,从高速公路水路流失的特点出发,指出边坡为公路水土流失重灾区。进行植物防护设计不仅能够达到防护效果,还有利于恢复植被,改善生态环境,有效地防止水土流失,并介绍了高速公路边坡水土流失植物防护技术设计原则。最后通过实践分析,对植物防护做出具体设计,为今后同类工程的水土保持措施布局提供参考和借鉴。     

Cost allocation by uniform traffic removal— Theoretical discussion and example highway cost applications

We propose four properties for equitable roadway cost allocations: (a) allocated costs should be based on full cost recovery, (b) allocated costs must be non-negative for any traveler group, (c) cost allocations should be additive, and (d) cost allocations should be consistent where equivalency factors among traffic categories exist. For cases with well-behaved cost functions, the uniform traffic removal technique discussed here uniquely satisfies these four properties and should be used whenever the four allocation properties are desired. Example applications as well as cases in which cost functions are not well behaved are discussed.     

山区高速公路常规桥梁设计要点分析

根据山区高速公路常规桥梁特点,提出了桥型方案的选择方法及设计原则,阐述了桥梁结构的设计要点。     

Optimal choice of capacity,toll and government guarantee for build-operate-transfer roads under asymmetric cost information

The private provision of public roads via the build-operate-transfer (BOT) mode has been increasingly used around the world. By viewing a BOT contract as a combination of road capacity, toll and government guarantee, this paper investigates optimal concession contract design under both symmetric and asymmetric information about the marginal maintenance cost of private investors. Under asymmetric information, the government guarantee serves as an instrument to induce a private investor to reveal his true cost information. Compared with the situation under symmetric information, the government will suffer a loss of social welfare; the private investor will charge a higher toll that increases in his reported marginal maintenance cost, and specify a lower capacity that decreases with the reported cost. The results also show that the private investor obtains extra information rent beyond the reservation level of return and the rent decreases with his reported cost. However, the resulting volume-capacity ratios of the BOT road under both information structures are the same.     

重视环保工作在公路建设中的地位及作用

通过公路工程施工中应当注意的环境保护问题,明确提出了环保工作在施工建设过程中的地位作用和注意事项。     

The speed control effect of highway tunnel sidewall markings based on color and temporal frequency

The low‐luminance monotonous environment in the middle section of highway tunnels offers few reference points and is prone to cause severe visual illusion. Thus, drivers tend to underestimate their driving speed, which can induce speeding behaviors that result in rear‐end collisions. Therefore, discovering low‐cost methods of traffic engineering that reduce this visual illusion and ensure a steady driving speed is an important challenge for current highway tunnel operations. This study analyzes the effects of sidewall markings in typical highway tunnels, specifically observing how their colors and temporal frequencies affect the driver's speed perception in a low‐luminance condition. A three‐dimensional model of the middle section of highway tunnels was built in a driving simulator. Psychophysical tests of speed perception were carried out by the method of limits. The precision of the simulation model was then checked by comparing the results to field test data. The simulation tests studied the stimulus of subjectively equal speed and reaction time in relation to sidewall markings in different colors (red–white combined, yellow–white combined, and blue–white combined). Furthermore, based on the optimal color, the effects of sidewall marking with different temporal frequencies (0.4, 0.8, 1.2, 2, 4, 8, 12, 16, and 32 Hz) on the speed perception of drivers were also analyzed. The test results reveal that the color and temporal frequency of sidewall marking have a significant impact on the driver's stimulus of subjectively equal speed and reaction time. The subjects have the highest speed overestimation and an easy speed judgment with the red–white combined sidewall marking. Within the temporal frequency range of 4.45–7.01 Hz, the subjects have a certain degree of speed overestimation (less than 20%), and the speed perception is sensitive to the temporal frequency changes. Copyright © 2016 John Wiley & Sons, Ltd.