Four-lane Highway Research Articles

국내 2+1차로 도로 도입에 따른 교통운영 및 경제적 비용 측면의 기대효과 분석

PURPOSES: The purpose of this paper is to estimate expected effects on traffic operational and economic aspects of 2+1 roads application in Korea. METHODS : Micro simulation study using VISSIM 5.0 was used to analyze the operation efficiency of 2+1 roads compared to two-lane highways and four-lane highways. Some scenarios for various traffic volumes were set up in order to analyze the effect of 2+1 roads under various traffic situations. Also imaginary road networks were set up for each type of roads. The MOEs to measure the operation efficiency were selected with average travel speed and delay. For analyzing economic effect of 2+1 roads, construction cost of a specific imaginary 2+1 road was compared to construction cost of a four-lane highway with same conditions. RESULTS: The results of study show that a 2+1 road is more effective with 19 percents higher average travel speed and 39 percents lower average delay than a two-lane highway. In the economic analysis, construction costs to construct a 2+1 road are saved as approximately 26.4~40.7 percents when compared to construction of four-lane highway. CONCLUSIONS: It can be concluded that 2+1 roads can improve the traffic operational level of service for two-lane highways and 2+1 roads can be applied as an effective design alternative for higher-volume two-lane highways in Korea.

Ipswich motorway, Australia: delivering transport solutions for urban corridors

The A$1·95 billion (£1·3 billion) Ipswich motorway upgrade near Brisbane was Australia's largest road infrastructure alliance. Origin Alliance – comprising the client, two designers and three contractors – was tasked with transforming an existing substandard four-lane motorway into a modern, intelligent six-lane highway with a future capacity for eight lanes using network-managed hard-shoulder running. Only 8·5 km long, the upgrade demanded an unprecedented level of temporary traffic management for up to 100 000 vehicles a day. This paper outlines the complexities in design and construction and the means by which works were planned to guarantee the utmost level of safety to the travelling public and on-site workforce.

Steel superstructure saves concrete arch bridge over the River Ohře, Czech Republic

AbstractThis paper describes the design and construction of the unique widening of a concrete arch bridge over the River Ohře using a lightweight steel superstructure. The bridge reconstruction formed part of the wider reconstruction measures for road I/6, including its upgrade from a two‐ to a four‐lane highway, near Loket between Nové Sedlo and Sokolov in the north‐west of the Czech Republic. Details of the erection of the steel structure and the strengthening of the concrete arch and piers are also given.

The Vascular Flora of Roadside Habitats in West Virginia, USA

In order to provide vegetation managers with information on roadside habitats in West Virginia, a statewide roadside vegetation study was conducted in 2000. The vegetation along nearly 1,500 km of four-lane highways was sampled in 339 randomly selected 20 m wide strip plots. An index of occurrence class (IOC) for each species was calculated using the product of the percent frequency of occurrence and relative abundance. A total of 467 species were documented, 325 of which were native. Seven families accounted for more than 50% of all species. When ranked on the basis of total IOC values, 15 of the top 25 species were introduced. Mean IOC values for introduced species (6.0) were significantly greater than native species (4.3, p = 0.0013). We propose that despite initial variability of landform, parent material, forest cover types, and climate, the relative similarity of species composition along the highways we sampled was the result of the physical and biological disturbances associated with initial construction (cuts and fills), and postconstruction seeding and vegetation management efforts.

Estimation of Diversion Rate during Incidents on Basis of Main-Line Detector Data

A number of intelligent transportation system technologies are deployed for disseminating information to travelers. One of the most important parameters for assessing the impacts and benefits of these deployments that influence route selection is the diversion rates of travelers. In this research, a method was developed to estimate traffic diversions on the basis of main-line detector data without the need for off-ramp detectors. In addition, the estimation allows the assessment of the guidelines and procedures for disseminating information and evaluating the impacts on alternative routes. The validity of the developed methodology was verified by comparing the estimated values with real-world data. Case studies of the developed method indicated that the average diversion rate was about 10% to 35% for three-lane and four-lane freeways, depending on the number of lanes blocked. A linear relationship between the average diversion rate and the lane blockage ratio was also developed; this relationship indicated that there was a general trend of increase in diversion with the increase in the lane blockage ratio.

Full versus Simple Safety Performance Functions

The empirical Bayes approach adopted in the Highway Safety Manual and the SafetyAnalyst software application require the use of safety performance functions (SPFs). SafetyAnalyst adopts a form of SPF, known as the simple SPF, that relates crash experience to traffic volume only. It is a flow-only model that is calibrated by using all sites irrespective of their base geometric conditions. Full SPFs, however, relate crash occurrence to roadway geometric characteristics in addition to traffic characteristics. This study compared the simple SPFs provided in SafetyAnalyst with full SPFs in two safety applications: crash prediction performance and identification of high-crash locations. To compare the prediction performance, the simple and full SPFs were estimated with data collected on urban four-lane freeway interchange influence areas in Florida. Models were estimated for both total crashes and fatal and injury crashes. The mean absolute deviance and the mean square prediction error were used to assess and compare the prediction performance of the two models, and the variation in ranking the high-crash locations with each model was also examined. The results showed that the two models yielded very similar performance of crash prediction and network screening. This empirical result supports the use of the flow-only SPF model adopted in SafetyAnalyst, whose development requires much less effort compared with that for full SPFs.

Evaluation of Continuous Green T-Intersections on Isolated Undersaturated Four-Lane Highways

The research presented in this paper analyzes the merging version of the continuous green T-intersection (CGT), an alternative intersection design–control that allows certain lanes along the main street to bypass three-way intersections, with side street traffic merging onto the main road. A comprehensive model encompassing 2,445 unique combinations of intersection conditions was run to compare the merging CGT with the standard three-way signalized intersection. The study demonstrated significant intersection improvements over conventional traffic signal timing. Specifically, significant benefits were observed for the merging CGT in total delay, fuel usage, and emissions of hydrocarbons, carbon monoxide, oxides of nitrogen, and carbon dioxide. In addition, an economic analysis showed significant user savings associated with CGT control. Because of higher traffic volumes on the main road than the side street, savings for vehicles on the main street outweighed any costs associated with side street traffic merging into the main street flow. These findings strongly support the decision to implement the merging CGT over standard three-way signalized intersection control. Before this work, no comprehensive model that considered the environmental and economic implications of any form of the CGT had been published, and no comprehensive model specifically focused on the merging version of the CGT.

The influence of curbs on driver behaviors in four-lane rural highways—A driving simulator based study

The speed limit of 55mph (88km/h) is typically used on rural highways in the U.S. For locations where curbs are installed along these roadways, some transportation agencies have suggested the use of a lower 45mph (72km/h) speed limit because, according to AASHTO, running into curbs at high speeds may cause significant vehicular damage and even severe injuries. However, it has also been argued that lowering the speed limit after the installation of curbs may cause confusion in drivers, who do not perceive the risk associated with the newly installed curbs and tend to operate their vehicles at the same speed as before.To better understand driver behavior on rural highways before and after curb installation, and with different speed limits, researchers at the University of Tennessee conducted a series of experiments in two-lane and four-lane highways on a high-fidelity driving simulator. This paper mainly presents the findings from the four-lane study, and compares the results from the previous two-lane study. The scenario matrix consists of several dimensions including posted speed limit (45 and 55mph, or 72 and 88km/h), curb installation, lateral clearance between the edge of travel lane and the curb (2ft, 6ft, and no-curb, or 0.6m, 1.8m, and no-curb), weather (clear and fog), traffic conditions in the next lane (1400veh/h and 400veh/h), etc. For each subject under different experimental scenarios, detailed driving parameters, such as driving speed and vehicle position in the travel lane, were recorded and analyzed subsequently.Results of the study suggest that driver behaviors are influenced by the various factors in a complex and interrelated manner. It is likely that drivers do not perceive the risk from the curb in determining their speed on four-lane rural highways. However, it is found that curbs may provide certain guidance to drivers, especially in selecting lane position. Compared to the previous research in two-lane conditions, it is found that drivers are more likely to choose driving speeds according to posted speed limits, rather than lane configurations. It is also found that the relative speed between driver's vehicle and ambient traffic or curbs is an important factor determining drivers’ perception of risk and thus their driving behavior. The influence of subjective effects of these factors to their driving behavior is also observed in the study.

Research on Traffic Characteristics and Traffic Conflicts of the One-Way-Closure Work Zone on Freeway

By analyzing the traffic characteristics and traffic conflicts of the typical one-way-closure work zone on four-lane freeway, the queuing characteristics of vehicles are determined, and the Erlang distribution model which can describe the distribution of time headway is calibrated. The speed distribution characteristics of each component of the work zone are concluded, and the speed limit scales for these components are put forward based on the statistic analysis. The types of traffic conflicts are firstly concluded, and then the identification method of the rear-end conflicts’ severity degree based on TTC technique as well as the prediction model of rear-end conflicts based on Negative Binomial distribution are put forward. The research results are useful to the analysis of traffic conditions of work zones, and they can also be used to evaluate the safety situations of freeway work zones

Effects of Vehicle Volume and Lane Closure Length on Construction Road User Costs in Rural Areas

The objective of this paper is to analyze the effects that vehicle volumes and lane closure lengths have on road user costs (RUCs) in rural freeway work zones. This paper presents a methodology developed to estimate RUCs for a rural four-lane freeway under construction with a single lane closure. Although the scenario presented is limited in its application to rural freeway construction projects, the methodology presented can be applied for any road construction project. Three tools have been developed as a result of this research: (a) a RUC template designed to calculate RUCs for a location on the basis of vehicle volumes, lane closure lengths, and speed values; (b) design graphs that practitioners can quickly reference to estimate RUCs for rural four-lane freeways with a single lane closure; and (c) regression equations derived from this research to quickly estimate RUCs. A practical and repeatable design method for estimating RUCs uses the results of this research. The design method can be used when time-based contractual provisions are developed on the basis of RUCs that are to be included in construction contracts for determining total project costs. When the method is used properly, it provides state highway agencies with a useful, justifiable way to calculate RUCs for single lane closure scenarios that can be used to develop incentive and disincentive provisions in rural roadway construction contracts.

Development of Left-Turn Lane Warrants for Unsignalized Intersections

Left-turn movements at intersections, including driveways—especially movements that are made from lanes that are shared with through traffic—cause delays and adversely affect safety. Although some left-turn warrants have been updated, many agencies still use research performed by M. D. Harmelink in the mid-1960s. Most states use procedures that are based on Harmelink's work, but several limitations have been identified. Economic analysis can provide a useful method for combining traffic operations and safety benefits of left-turn lanes to identify situations in which left-turn lanes either are or are not justified economically. This project used a benefit–cost approach to determine when a left-turn lane would be justified. The steps included simulation to determine delay savings from installing a left-turn lane, crash costs and crash reduction savings determined from safety performance functions and crash modification factors available in the Highway Safety Manual, and construction costs. Left-turn lane warrants were developed for rural two-lane highways, rural four-lane highways, and urban and suburban roadways. In addition, warrants for bypass lanes were developed for rural two-lane highways.

Speed Prediction Models for Multilane Highways: Simultaneous Equations Approach

Past speed-related research has focused on the operational effects of roadway geometrics along rural two-lane highways using ordinary least-squares regression models. More recent research has focused on the association of traffic flow characteristics on vehicle operating speeds along multilane, limited access highways using a simultaneous equations approach. Few research studies, however, have been conducted to determine the combined association between various geometric design features and traffic flow on operating speeds along multilane highways. This research considers both geometric design and traffic flow parameters, in a simultaneous equations framework, to model the mean operating speed and speed deviation on four-lane highways (two lanes in each direction). Models for both left- and right-lane mean speeds and speed deviations were estimated. The three-stage least-squares estimator was used to investigate the possible endogeneity of mean speed and speed deviation in the system of equations and to account for the contemporaneous correlation between the disturbances across the equations. The results indicate that different geometric design features are associated with mean speed and speed deviation in the left- and right-lane models. As such, it is recommended that future multilane highway speed models consider using a simultaneous equations framework.

Horizontal Curve Accident Modification Factor with Consideration of Driveway Density on Rural Four-Lane Highways in Texas

Agencies are seeking a better understanding of those roadway or roadside features that affect safety. The objectives of this study were to develop a horizontal curve accident modification factor (AMF) for rural four-lane divided and undivided highways and to determine if the effect of driveway density is different for horizontal curves as compared to tangent sections. Data available for use in the evaluation included 194.8 centerline km (121 centerline mi) of rural four-lane highways. Negative binomial regression models were used to determine the effects of independent variables on crashes. Variables considered in developing the base models included driveway density, lane width, outside shoulder width, median width (which included inside shoulder width), median type, degree of curve, segment length, and average daily traffic. Five years (1997–2001) of driveway and segment crashes were examined. An AMF for horizontal curves was identified. Reviewing the findings with respect to driveway density revealed that the effect of driveway density is different for horizontal curves and tangents; however, the differences were relatively minor.

Response of benthic macroinvertebrate communities to highway construction in an Appalachian watershed

Highway construction in mountainous areas can result in sedimentation of streams, negatively impacting stream habitat, water quality, and biotic communities. We assessed the impacts of construction of a segment of Corridor H, a four-lane highway, in the Lost River watershed, West Virginia, by monitoring benthic macroinvertebrate communities and water quality, before, during, and after highway construction and prior to highway use at upstream and downstream sites from 1997 through 2007. Data analysis of temporal impacts of highway construction followed a Before-After-Control-Impact (BACI) study design. Highway construction impacts included an increase in stream sedimentation during the construction phase. This was indicated by an increase in turbidity and total suspended solids. Benthic macroinvertebrate metrics indicated a community more tolerant during and after construction than in the period before construction. The percent of Chironomidae and the Hilsenhoff Biotic Index (HBI) increased, while percent of Ephemeroptera, Plecoptera, and Trichoptera (EPT) decreased. Our 10-year study addressed short-term impacts of highway construction and found that impacts were relatively minimal. A recovery of the number of EPT taxa collected after construction indicated that the benthic macroinvertebrate community may be recovering from impacts of highway construction. However, this study only addressed a period of 3 years before, 3 years during, and 4 years post construction. Inferences cannot be made concerning the long-term impacts of the highway, highway traffic, runoff, and other factors associated with highway use. Continual monitoring of the watershed is necessary to determine if the highway has a continual impact on stream habitat, water quality, and biotic integrity.

Node-island, multi-layer self-balanced Archimedes Bridge

A preliminary structure scheme is proposed on a node-island, multi-layer self-balanced Archimedes Bridge upon which two track rails and a four-lane highway could be established. Some analysis has been made on its mechanical characteristics, vibration, corrosion, security and economy. Using this conceptual construction program, transport channel options for the Taiwan Strait are discussed according to the hydrological and geological conditions of the Taiwan Strait.

Impact of Rumble Strips on Collision Reduction on Highways in British Columbia, Canada: Comprehensive Before-and-After Safety Study

A comprehensive before-and-after study evaluated the safety impacts associated with application of shoulder and centerline rumble strips on highways in British Columbia, Canada. Data were collected for three groups of sites: treatment group, comparison group, and reference group. The treatment group included 47 sites belonging to two highway classes: an undivided, rural two-lane arterial (RAU2) and a divided, rural four-lane freeway. A total of 225 sites were used to establish a comparison group for the treatment sites based on implementation year for the treatment site and the highway class. The comparison group was used to correct for the confounding factors of history and maturation. Six reference groups were used; they correspond to the two highway classes and three time periods (2000 to 2002, 2001 to 2003, and 2002 to 2004). Collision prediction models developed from the reference groups were used to correct for the regression to the mean and to account for the changes in traffic volumes in the before-and-after periods. Overall, the results showed that shoulder and centerline rumble strips can significantly reduce severe collisions and specific collision types: (a) the installation of rumble strips reduced all injury collisions by a statistically significant 18.0%; (b) shoulder rumble strips reduced off-road right collisions by a statistically significant 22.5%; and (c) centerline rumble strips (RAU2 sites) showed a statistically significant reduction of 29.3% in off-road left and head-on collisions. RAU2 sites with both centerline and shoulder rumble strips showed a statistically significant reduction of 21.4% in off-road right, off-road left, and head-on collisions combined.

Comparison of Application of Product of Baseline Models and Accident-Modification Factors and Models with Covariates: Predicted Mean Values and Variance

Research was done to compare the application of full models (or models with several covariates) and baseline models, estimated by using data meeting specific nominal conditions combined with accident-modification factors (AMFs) for predicting motor vehicle crashes. The analysis focuses on the predicted values and associated inferences for both types of models. In the past few years, researchers have questioned the approach of multiplying baseline models with AMFs. For comparison, full and baseline models are estimated by using data collected on rural four-lane highways in Texas. AMFs describing the safety effects related to lane and shoulder width as well as the number of horizontal curves per mile are extracted from previous work. Two scenarios describing AMF values and their associated uncertainty are evaluated. The results of the study show that the product of baseline models and AMFs produces a much larger variance, hence a wider 95% predicted confidence interval, than the variance calculated using the full models. This is consistent for the two scenarios evaluated and for all levels of uncertainty associated with the AMFs. The study concludes that the full model should be used instead of the product of the baseline model and AMFs when the study objective includes variance as part of the decision-making process.

Using occupancy models to determine mammalian responses to landscape changes

Determining impacts of anthropogenic landscape changes on wildlife populations is difficult. Besides the challenges of designing field studies to document conditions before and after landscape changes occur, assessment of population responses (e.g. changes in population density) often provide poor inference because of sampling limitations. Estimation of occupancy, however, only requires data on detection or non-detection of a species and might provide better inference. To demonstrate the utility of occupancy models, we used data from an American black bear (Ursus americanus Pallas) population in North Carolina, USA to test our research hypothesis that documented declines in site occupancy of black bears would be greater near a new four-lane highway. We used multi-season occupancy models to estimate site occupancy based on bear visitation to survey sites before and after completion of the new highway and as a function of distance to the highway. Site occupancy declined from 0.81 to 0.35 between the two study phases, but was not a function of distance to the highway. Therefore, the impact of the new highway on occupancy extended to the entire study area. Our case study demonstrates that occupancy models can provide powerful inference regarding the potential impacts of landscape changes on species occupancy. As urban areas and transportation infrastructure are rapidly expanding in developing regions of the world, the need to determine how these changes affect mammal populations and how they might be mitigated increases accordingly. Because field sampling for occupancy models only requires detection data, surveys can be conducted for extensive geographic areas, thus making these surveys particularly applicable to studies of large mammals.

Multichannel Medium Access Control for Dedicated Short-Range Communications

This paper describes a medium access control (MAC) protocol to enable multichannel operation for dedicated short-range communications (DSRCs). In particular, we focus on the challenge of supporting potentially high-bandwidth commercial or infotainment communications between vehicles and the roadside in hotspots over several service channels, while concurrently enabling time-critical vehicle-vehicle communications for safety in a separate channel. In our architecture, within hotspots, the communication is aided by one of the access points in the hotspot. This access point is designated as the coordinating access point (CAP). Outside the hotspots, the communication is for safety only and is conducted in an ad hoc fashion. The CAP protocol design leverages IEEE 802.11 point coordination function (PCF) and distributed coordination function (DCF), which are modified for multichannel operation. The design objective is to maximize the utilization of the service channel that is used for nonsafety communications while meeting the quality-of-service (QoS) constraints of the safety communications. The performance of the IEEE 802.11 DCF and PCF and the CAP extension is quantified by simulation in NS-2. The mobility model represents a four-lane freeway at maximum vehicular traffic flow that is derived from the SHIFT traffic simulator. The CAP design is shown to significantly enhance the performance of safety and nonsafety communications.

Effect of Truck Lane Restrictions on Four-Lane Freeways in Mountainous Areas

Several states have implemented truck lane restrictions in an attempt to improve safety and mobility on freeways. These restrictions have typically prohibited trucks from traveling in the median lane of freeways that have more than three lanes per direction. Virginia has recently implemented a new type of truck restriction that prohibits trucks traveling more than 15 mph below the posted speed limit from the left lane on four-lane interstate segments. This new restriction is primarily used in mountainous areas of the state where truck climbing lanes may be warranted but are not present. The results of a safety and operational evaluation of these truck lane restrictions were documented. Crash data were examined at 19 sites with restrictions. Likewise, operational data were collected at four sites with restrictions to assess compliance and the extent to which slow-moving trucks were impeding traffic flow. The safety analysis shows some positive trends in crash rates after implementation of the restrictions, but only the overall number of fatal and injury crashes showed a statistically significant decline. Although compliance with the restrictions was generally good, a number of slow-moving vehicles, including passenger cars, were still found to be impeding traffic in the left lane.