bluuebunny/crossref_metadata_2025 huggingface dataset:
Commuter Behavior on California State Route 91 After Introducing Variable-Toll Express Lanes
Authors: Mastako Kimberley , Rillet Laurence R. , Sullivan Edward C.
Published: April 2007

In December 1995, four new variable-toll express lanes were added to the median of a 16-km segment of California State Route 91 (SR-91). For those willing to pay the tolls, the new lanes provide an option to bypass congestion on the regular lanes. A special provision has initially allowed three-plus occupant vehicles to travel the congestion-free facility free of charge. A telephone survey of SR-91 travelers taken in fall 1996 provides insight as to how peak-period, peak-direction work commuters have responded to the new express lanes. Responses of 324 interviewed commuters are analyzed for changes in ridesharing, trends in express lane use, and differences in travel behavior among various socioeconomic groups. This research is important because public concern about fairness is a significant obstacle to the implementation of lane pricing. Two approaches are used to analyze changes in ridesharing and express lane usage. One approach focuses on usual travel behavior; the other focuses on the most recent work trip. The results of both approaches suggest that there has been an overall shift by commuters from lower to higher occupancy vehicles since the opening of the express lanes, and that express lane usage increases as the per person modal cost decreases. An aggregate analysis indicates that 23 percent of SR-91 commuters use the express lane for most of their work trips, and 46 percent never use the lanes. Statistical tests indicate that among two-occupant-vehicle commuters, household income influences express lane usage, and that among single-occupant-vehicle commuters, household type influences express lane usage.
Scheduling of Pavement Maintenance To Minimize Traffic Delays
Authors: Fwa T. F. , Cheu R. L. , Muntasir A.
Published: April 2007

Traffic delays caused by pavement maintenance activities are a major concern to transportation engineers. There is a need to carefully plan and schedule such activities in order to minimize traffic delays. Unfortunately, this is a complex problem that cannot be easily solved by means of conventional optimization tools. A scheduling methodology is presented that uses genetic algorithms (GAs) to minimize traffic delays subject to constraints of maintenance operational requirements. The flexibility in problem modeling and the robust search capability of the GA technique make it a practical analytical tool for this problem. Pavement distress conditions, traffic flow data, and maintenance requirements are the major input parameters of the problem. Based on Singapore’s maintenance practice and traffic delay models for four-lane two-way primary roads, a computer program has been developed. This program is applied to solve a hypothetical numerical example problem to illustrate the formulation and solution procedure of the proposed methodology.
Crash Testing and Evaluation of Work Zone Traffic Control Devices
Authors: Mak King K. , Bligh Roger P. , Rhodes Lewis R.
Published: April 2007

Safety of work zones is a major area of concern since it is not always possible to maintain a level of safety comparable to that of a normal highway not under construction. Proper traffic control is critical to the safety of work zones. However, traffic control devices themselves may pose a safety hazard when impacted by errant vehicles. The impact performance of many work zone traffic control devices is mostly unknown, and little, if any, crash testing has been conducted in accordance with guidelines set forth in NCHRP Report 350. The Texas Department of Transportation (TxDOT) has, in recent years, sponsored a number of studies at the Texas Transportation Institute to assess the impact performance of various work zone traffic control devices, including plastic drums and sign substrates, temporary and portable sign supports, plastic cones, vertical panels, and barricades. The results, findings, conclusions, and recommendations are presented for temporary and portable sign supports, plastic drums, sign substrates for use with plastic drums, traffic cones, and vertical panels, whereas those for barricades are covered elsewhere. Most of the work zone traffic control devices satisfactorily met the evaluation criteria set forth in NCHRP Report 350 and are recommended for field implementation. However, some of the devices failed to perform satisfactorily and are not recommended for field applications. The results from these studies are being incorporated into the TxDOT barricade and construction standard sheets for use in work zones.
Optimum Length of Single-Lane Closures in Work Zones on Rural Four-Lane Freeways
Authors: Mccoy Patrick T. , Mennenga David J.
Published: April 2007

The lengths of single-lane closures in work zones on rural four-lane freeways are commonly based on the expected work rate in order to avoid moving the temporary traffic control zone more frequently than once a day and to limit the possibility of interfering with the work activity. However, the analysis presented suggests that this practice may result in single-lane closures that are ( a) longer than the lengths that would minimize the sum of the additional road user and traffic control costs and ( b) shorter than those that would minimize the traffic control cost. The objective of the analysis presented is to determine the optimum length of single-lane closures in long-term-stationary temporary traffic control zones on rural four-lane freeways that minimizes the sum of the additional road user and traffic control costs associated with the temporary traffic control zone. An equation for the optimum length is derived using the methods of calculus. The equation can be used to determine the most cost-effective and the most economical lengths of single-lane closures on rural four-lane freeways.
Influence of Exposure Duration on the Effectiveness of Changeable-Message Signs in Controlling Vehicle Speeds at Work Zones
Authors: Garber Nicholas J. , Srinivasan Srivatsan
Published: April 2007

In work zones, drivers do not slow down in response to conventional signs. Changeable-message signs (CMSs) equipped with a radar unit can be used to display specific warning messages to speeding drivers. The radar unit detects the speed of each vehicle entering the work zone and can be programmed to activate the CMS if the speed of the vehicle exceeds a preset threshold value. A two-phase longitudinal study was conducted. The first phase, conducted by Garber and Patel, examined the short-term effectiveness of the CMS with radar in reducing vehicle speeds in work zones. The second phase, some of the results of which are presented, evaluated the influence of the duration of exposure of the CMS with radar on its effectiveness in reducing speeds in work zones. Speed and volume data for the population were collected at the study sites by automatic traffic counters placed at the beginning, middle, and end of each work zone. In addition, the speeds of individual drivers who triggered the CMS by exceeding the threshold speed were also recorded (using a video camera) at two other locations within the work zone for several weeks and analyzed. The results of the study indicated that the duration of exposure of the CMS does not have a significant impact on speed characteristics and driver behavior. Therefore, the CMS continues to be effective in controlling speeds in work zones for projects of long duration. The results also indicated that the CMS with radar reduces the probability of speeding at work zones and that this effect is maintained for at least up to 7 weeks.
Incorporating Intelligent Transportation Systems into Major Investment Studies: Conceptual Issues and Challenges
Authors: Gregory Hatcher S. , Bunch James A. , Roberts Donald L.
Published: April 2007

The issues associated with incorporating intelligent transportation systems (ITS) strategies into alternatives analysis planning studies such as major investment studies (MIS), which have emerged since the Intermodal Surface Transportation Efficiency Act was passed in 1991, are discussed. The challenges and implications of including ITS in three of the key steps of the MIS process—problem definition, alternative definition, and analysis—are examined. As context for the specific issues addressed, a case study is presented on incorporating ITS into a corridor planning process that is being conducted using Seattle data. Critical to incorporating ITS elements within an MIS process is developing a problem statement, goals and objectives, and measures of effectiveness that are sensitive to ITS and other operational improvements for the corridor or subarea under study. Traditional MIS processes have focused on facility/service improvements and on average conditions and demand. ITS strategies, on the other hand, aim at improving ( a) operations; ( b) response to nonrecurrent conditions; and ( c) providing better information. To be able to address ITS strategies, the analysis approach used in an MIS should be sensitive to these issues. An illustration of how ITS strategies are being incorporated and evaluated in the Seattle (MIS-like) case study concludes the discussion.
Intermediate Automation Concepts for Incremental Deployment of Automated Highway Systems
Authors: Alkadri Mohamed , Benouar Hamed , Jacob Tsao H.-S.
Published: April 2007

Automated highway systems (AHS) are a promising concept whose implementation needs to take place in a modular and incremental manner. Immediate implementation of a fully automated highway system may not be feasible or desirable. It does not allow for the necessary testing and evolution of technology, markets, and social change. Recognizing the importance and challenge of progressive, evolutionary AHS deployment, six deployment assumptions are presented, three deployment issues are discussed, and several intermediate automation concepts for evolution toward AHS are proposed. Concepts are presented in the form of “market packages.” Some of these concepts are simple driver aiding systems; others are capable of supporting hands-off and feet-off driving. In the evolutionary path to AHS, a number of comfort and safety enhancements could be realized initially without large infrastructure modifications and without dedicated lanes. Intermediate deployment steps are necessary to help early deployment of partial automation, to allow AHS technology to mature, to establish user confidence, and to create market demand and public acceptance. The packages presented are designed so that they attract the driving public with comfort and safety benefits while requiring no significant roadway infrastructure modification and they encourage motorists to purchase (or retrofit) vehicles with equipment that enables hands-off and feet-off driving, thus building confidence in and creating demand for AHS.
Economic Decision Model for Low-Volume Roads
Authors: Archondo-Callao Rodrigo
Published: April 2007

Presented is the low-volume roads economic decision model (RED), developed to improve the decision-making process for the development and maintenance of low-volume roads of key importance in Africa. The model performs an economic evaluation of road investment options by using the consumer surplus approach. It is customized to the characteristics of low-volume roads such as the high uncertainty of assessment of model inputs, particularly traffic and the condition of unpaved roads, the importance of travel times for model validation, and the need for a comprehensive analysis of generated traffic, and to clearly define all accrued benefits. RED computes benefits for normal, generated, and diverted traffic and takes into account changes in road length, condition, geometry, type, accidents, and days per year when the passage of vehicles is further disrupted by a highly deteriorated road condition. Users can add other benefits to the analysis, such as nonmotorized traffic, social services, and environmental effects, if computed separately. The model is presented on a series of Excel 5.0 workbooks that collect all user inputs, present the results efficiently, and perform sensitivity, switching values, and stochastic risk analyses. The model soon will be subject to empirical testing using data from selected countries.
User-Friendly Model for Planning Rural Roads
Authors: Kumar Ashok , Kumar Praveen
Published: April 2007

India faces a very tough challenge to provide an adequate road network to its villages under serious constraints of funds. Present planning practices of rural roads mostly are based on ad hoc approaches, which leads to suboptimal utilization of funds. Presented is a user-friendly model for systematic planning of rural road networks that increases the efficiency of available resources for rural roads. The model provides an all-weather road connection from each village to nearby market centers and education centers at the least cost by generating an optimal rural road network. The model is computer based, which facilitates its effective application. It generates an optimal rural road network by using a heuristic approach that minimizes total transportation cost of the network. The model can be used effectively for preparation of master plans of rural roads. The tasks that can be performed by the model include ( a) identifying the requirements of fresh road construction; ( b) identifying the need for upgrade of an existing road network; ( c) selecting appropriate design and construction standards; ( d) identifying important missing bridges and missing links from an existing rural road network; and ( e) identifying priority links for maintenance in an existing rural road network. Practical applications of the model demonstrate significant advantages over the prevailing practices of rural road planning in India.
Better Management of Local Roads Through Effective Technology Transfer
Authors: Giummarra George
Published: April 2007

Australia is a vast country with diverse environmental conditions ranging from mountainous to flat terrain, from large deserts to tropical areas with varying soil types, rainfall, and traffic conditions. The total road network in Australia is about 900 000 km, with more than 85 percent made up of local roads. This requirement places heavy demands on the development and maintenance of our road network for a sparse population of over 18 million and with limited resources. Local governments across Australia are in need of practical and understandable solutions to the many road transport problems they face. Coupled with this is the need to better manage road assets to gain maximum benefit from the limited road funding available. In late 1991 ARRB Transport Research Ltd. began an active technology transfer program aimed at helping the local road practitioners improve the performance of their road assets by making greater use of the latest developments, research findings, and provision of technology transfer services. Highlighted is how ARRB Transport Research is working with local government and other agencies responsible for local roads to put research, new developments, and services into the hands of practitioners so as to better manage local road assets. Addressed are the establishment of practitioners’ road needs, delivery of research to meet the specific needs of local roads, development of numerous technology transfer activities, and reported benefits of the activities undertaken.
Accident Characteristics on Low-Volume Roads in Indonesia
Authors: Achwan Nawawi , Rudjito Didik
Published: April 2007

Road accident statistics from the Indonesian Traffic Police Headquarters for the last decade show that there have been 10,000 fatalities on average per year. This situation has become a serious national issue. Since 1989 the Overseas Unit of Transport Research Laboratory has been involved in a collaborative research study on road safety with the Institute of Road Engineering in Bandung, using the Microcomputer Accident Analysis Package (MAAP). A pilot study to implement the MAAP system was set up in four regions. The characteristics of road accidents on selected low-volume roads are described and processes for identifying contributory factors at hazardous locations are introduced.
Incremental Safety Improvements for Unpaved Rural Roads
Authors: Calvert Eugene C. , Wilson Eugene M.
Published: April 2007

With limited resources and increasing exposure to tort liability, local rural road agencies face the dilemma of how to maximize improvements to their road system. For unpaved rural roads the problem is particularly acute. Many of these unpaved rural roads worldwide have geometric deficiencies that do not conform with recognized standards and guidelines. In many instances, roadway improvements are not being completed because of the inability to fund improvements to meet these standards and guidelines. Incremental improvements for unpaved rural roads is potentially an important tool for local agencies. The goal is at least to meet minimum guidelines and standards by continuing to implement an incremental program. Reported here are the results of a project that used a national U.S. focus group to provide input into the acceptability of the concept and use of incremental safety improvements on unpaved rural roads. The investigation targeted horizontal curvature as a site deficiency. The focus group was used to identify if and what incremental improvements should be considered. The results demonstrated the need for functional subclassifications of rural unpaved roads, with incremental decisions made that address the unique operational differences. Incremental improvements, when properly considered, are recommended as an acceptable method to increase safety on unpaved rural roads and to minimize liability.
Design of Falls Creek Trail Bridge: A Fiber Reinforced Polymer Composite Bridge
Authors: Wallace Scott
Published: April 2007

The need for lightweight, low-maintenance, easily constructed bridges for remote locations has existed for a long time. The backcountry of forests and parks throughout the United States is made accessible by trail systems that often encounter streams, rivers, gorges, and other features that must be spanned. Because of their remote locations, conventional approaches to spanning these barriers often are impractical. The Eastern Federal Lands Highway Division of FHWA, in conjunction with the United States Forest Service and with assistance from E.T. Techtonics, designed, tested, and constructed a pedestrian trail bridge 13.9 m (45.5 ft) long made of fiber reinforced polymer (FRP) composite members. Development of design procedures for this type of bridge is presented. The initial load testing results used to evaluate the analysis and design of the structure are presented and future construction plans for this bridge are mentioned. Attractive characteristics of FRP composites for construction of pedestrian trail bridges and shortcomings are illustrated. Further testing and research of the Falls Creek Trail bridge are ongoing and further testing and research of FRP composites also are needed. Advances in the understanding of currently available materials, as well as advances in the materials themselves, likely will affect structural design methods and procedures in the future. However, on the basis of available data, FRP composites appear to be well suited to meeting the need for backcountry trail bridges.
Use of Soft Limestone for Road-Base Construction in Belize
Authors: Woodbridge M. E.
Published: April 2007

The results of a highway experiment, constructed in May 1978 in northern Belize, designed to investigate the suitability of locally occurring calcareous materials, known as marls, for road bases are discussed. The marls comprise high-purity carbonate materials containing mainly siltsized particles and fall outside the grading, plasticity, and strength specifications normally required for road bases. Three marls, each with slightly different characteristics, were substituted as road base for crushed stone. One of the marls was also stabilized with ordinary portland cement. Detailed monitoring was then undertaken periodically to determine their performance. The road pavement was constructed on an embankment to ensure good drainage. A good quality surface dressing seal has been maintained. After 19 years of traffic, measured at 1.3 million equivalent standard axles, the marl road bases have performed at least as well as the crushed stone. The cement-stabilized marl road base performed exceptionally well. Stabilization would enable the use of more plastic marls.
Use of Ash in Low-Volume Road Construction in South Africa
Authors: Heath Andrew , Theyse Hechter , Lea Jeremy
Published: April 2007

Sasol Chemical Industries produces large quantities of coarse clinker and fly ash as a by-product of the coal gasification process at their Sasolburg plant in South Africa. If this ash could be used as an aggregate in roads, the demand on natural reserves for aggregates would be reduced and an effective method of disposing of these materials would result. The ash is processed at a blending plant in Sasolburg and is marketed under the name Premamix. Trial sections were constructed using labor-based techniques with unstabilized and bitumen emulsion-treated Premamix as a base course material. As the Premamix is a lightweight material and is delivered at a specified moisture content (the optimum moisture content for compaction), it is ideal for labor-based construction of low-volume roads as only spreading and compaction of the layers are required. The trial sections were subjected to accelerated pavement testing with the heavy-vehicle simulator. Although high deflections were measured in the pavement structure, the Premamix performed well under trafficking, even after the base was soaked with water.
Evaluation of Resilient Modulus of Subgrade Soil by Cone Penetration Test
Authors: Mohammad Louay N. , Titi Hani H. , Herath Ananda
Published: April 2007

Pavement design based on the resilient modulus of subgrade soil has been adopted by many transportation agencies following the recommendations of the AASHTO guide for design of pavement structures. Laboratory and field nondestructive tests are generally used to evaluate the resilient modulus of subgrade soil. These methods have shortcomings and limitations and are considered laborious, time-consuming, and expensive. The difficulties associated with the existing methods signify the need for a popular in situ technology for evaluating the resilient modulus of subgrade soil. Among other methods, the cone penetration test (CPT) is fast, simple, and economical and provides repeatable and reliable results. The results of a pilot investigation to assess the possibility of predicting the resilient modulus of subgrade soil from the CPT soundings are presented here. Field and laboratory testing programs were carried out on two types of cohesive soils at the Louisiana Transportation Research Center/Pavement Research Facility. Field tests consisted of CPT soundings using the 15-cm2 friction cone penetrometer and the 2-cm2 miniature friction cone penetrometer. Laboratory tests included the resilient modulus and physical properties of the investigated soils. The results of the miniature CPT were evaluated and compared with the soundings of the 15-cm2 cone at the same site. Both laboratory and field tests were analyzed. Based on statistical analyses, a model was proposed to estimate the resilient modulus from the CPT data and basic soil properties. Predicted values of the resilient modulus are consistent with laboratory measurements.
Utilization of Industrial Wastes in Low-Volume Roads
Authors: Mathur Sudhir , Soni S. K. , Murty Avsr
Published: April 2007

In recent years, applications of marginal materials, also called nontraditional (either natural or waste products), have been considered in road construction with great interest in many industrialized and developing countries. The use of nontraditional materials in road making is based on technical, economic, and ecological criteria. The lack of traditional road materials and the protection of the environment make it imperative to investigate marginal materials carefully. India has a large network of steel plants located in different parts of the country and many more are planned for the near future. Several million metric tons of iron and steel are produced in these plants. However, along with production of iron and steel, huge quantities of solid wastes like blast furnace slag and steel slag as well as other wastes such as flue dust, blast furnace sludge, and refractories are also being produced in these plants. The iron ores in India, although rich in iron content, are high in alumina content also and as such the volume of slag generated is very high. Normally production of 1 metric ton (1 Mg) of steel generates 1 Mg of solid waste. Although the steel industry slags have their own unique properties and are exploitable for road works, they have never been put to use on Indian roads because of a lack of scientific studies conducted on these materials, nonavailability of proper design and construction standards on them, and the absence of data about the long-term behavior of these materials. In the absence other outlets, these solid wastes have occupied several acres of land around plants throughout the country. Keeping in mind the need for bulk use of these solid wastes in India, it was thought expedient to test these materials and to develop specifications to enhance the use of slags in road making, in which higher economic returns may be possible. Exhaustive and detailed laboratory investigations have been carried out at the Central Road Research Institute, New Delhi, India, to develop suitable specifications for construction of low-volume roads. Based on laboratory investigation results, specifications were developed for construction of low-volume roads in different parts of the country. While specifications were being formulated, attempts were made to maximize use of solid wastes in different layers of the road pavement. Postconstruction pavement performance studies have clearly indicated that these waste materials can be used for construction of low-volume roads with twofold benefits: ( a) it will help clear valuable land of huge dumps of slags, and ( b) it will also help preserve the natural reserves of aggregates, thus protecting the environment.
Evaluation of Reclaimed Asphalt Pavement Aggregate in Road Bases and Subbases
Authors: Taha Ramzi , Ali Galal , Basma Adnan , Al-Turk Omar
Published: April 2007

Recycling of pavement materials has become a viable alternative to be considered in road maintenance and rehabilitation. Conservation of resources, preservation of the environment, and retention of existing highway geometrics are some of the benefits obtained by reusing pavement materials. In the United States of America, more than 50 million tons (45.36 million Mg) of asphalt paving material are milled annually; recycling into new asphalt paving mixtures is the predominant application. However, large quantities of reclaimed asphalt pavement (RAP) aggregate remain unutilized and further uses should be explored. In the Sultanate of Oman, recycling of pavement materials is not practiced; this study presents a first attempt at evaluating RAP aggregate. The reuse of RAP aggregate could be economically attractive in Oman because certain regions of the country experience virgin aggregate shortage. Furthermore, rehabilitation of the road network would provide a valuable resource to be considered in highway construction. A laboratory evaluation of RAP and RAP-virgin aggregate mixtures as road base and subbase materials is described here. Physical, compaction, and California bearing ratio tests were conducted on the following RAP/virgin aggregate blends: 100/0, 80/20, 60/40, 40/60, 20/80, and 0/100 percent. Initial results indicate that RAP could be expected to replace virgin aggregate in the pavement subbase structure with satisfactory results if the RAP material were mixed with virgin aggregate. Best results were obtained for the 60/40, 40/60, 20/80, and 0/100 percent RAP/virgin aggregate blends. Higher dry density and CBR values are obtained as virgin aggregate content is increased. Based on a comparison with standard paving materials used in the Sultanate of Oman roads, the stabilized RAP material appears to be able to function as well as a conventional subbase material. However, only minimal use of RAP (about 10 percent) can be expected in road bases.
Laboratory Testing of Nontraditional Additives for Stabilization of Roads and Trail Surfaces
Authors: Bolander Peter
Published: April 2007

Recently the Pacific Northwest Region of the U.S. Department of Agriculture Forest Service conducted laboratory tests evaluating the expected field performance of various additives on dense-graded aggregate. Additives used in the laboratory analysis included chlorides, clay, enzymes, lignin sulfonate, synthetic polymer emulsions, and tall oil emulsions. Laboratory analysis included indirect tensile strength and durability testing on AASHTO T 99 fabricated samples. Durability was evaluated after a number of wet-dry and freeze-thaw cycles. Other variables in the study included the amount of additive and the cure (temperature and time) before testing. Findings and observations include the following: (a) Untreated dense-graded aggregate provides little tensile strength in warm dry climates, (b) Chlorides, clay additives, enzymes, and sulfonate provide some tensile strength in warm dry climates. With increasing moisture contents they lose their tensile strength, (c) Once cured, synthetic polymer and tall oil emulsions provide significant tensile strength in warm dry climates. In wet climates these additives would tend to break down with increased exposure to moisture or freezing. (d) Increasing the percent residual (solids) of the synthetic polymer emulsions and tall oil emulsions increases the tensile strength and durability of the treated material, (e) Cure temperature has a dramatic impact on tall oil emulsions’ tensile strength and durability resistance. (f) The use of nontraditional additives can be cost-effective depending on the projects’ objective, the type of in-place material, and the cost of the additive.
New Specification of Material for Surfacing Unpaved Roads
Authors: D’ávila Alfredo L. M. , Sória Manoel H. A. , Jorge Roberlaine R.
Published: April 2007

To develop a new specification of material for surfacing unpaved roads, an experiment was conducted on 41 unpaved road sections located in five different physiographical regions in the state of Rio Grande do Sul, Brazil. The behavior of the sections under observation was analyzed qualitatively to evaluate the performance of the applied surfacing material. Because the traditional soil classifications (Highway Research Board and Unified Soil Classification System) are not suitable for classifying tropical soils, a new classification, namely MCT (miniature, compacted, tropical), developed in Brazil in 1981 was adopted as a basis for material selection. The behavior parameters observed were support, frictional resistance, and durability. The results obtained led to the specifications presented here, which were tested during a doctorate research program developed between 1991 and 1996 conducted by the first author and supervised by the second. It was concluded that the proposed specification based on the MCT classification system is more adequate than the ones previously used based on traditional classifications. The “binder content” of soils, a measure similar to that used for bituminous materials (asphalt binder content) is introduced to evaluate the agglomerating capacity of the fine fraction and, therefore, the material durability.
Scheduling and Management Improvements Accelerate Roadway Design
Authors: Dolson Gregory A.
Published: April 2007

The Federal Highway Administration’s Eastern Federal Lands Highway Division has been actively involved over the past 10 years with the development of a process to maintain better control of its design project schedules. Three initiatives were undertaken during this time period. The first initiative involved a change in structural organization by establishing a strong project management concept from a project’s inception to its construction contract award. The second initiative recognized early on that a well-scheduled project eliminates many of the problems encountered during the design process. The resulting scheduling resource system became a valuable tool for the project managers. In the third initiative, a team developed a road map of the design process to better serve the division’s customers. After 10 years, customer satisfaction is improving, project schedules are under better control, and improvements to the design process have resulted in timely and cost-efficient projects.
Construction of Vertical Moisture Barriers To Reduce Expansive Soil Subgrade Movement
Authors: Evans R. P. , Mcmanus K. J.
Published: April 2007

Throughout the world, expansive soils are known to cause damage to light structures, such as residential dwellings, road pavements, and airfields. In Australia, moderate to highly expansive soils cover more than half the state of Victoria and produce significant maintenance problems to the state’s road network. Vertical moisture barriers have been used successfully in many cases across the United States to control movements generated from expansive soil subgrades. Field trials using moisture barriers have also been conducted successfully in Victoria, Australia. However, due to their expense, the treatment of using vertical moisture barriers has usually only been reserved for major highways. A review of current vertical moisture barrier construction methods in the United States is made, and a new construction method developed in Victoria that provides an effective and economical barrier is reported. This method will enable the application of vertical moisture barriers to be more attractive for sealed low-volume roads. A successful field trial of this construction method has been carried out at Dooen, in northwest Victoria, and has since been applied to several other projects in Victoria and South Australia.
Simple Approach to Estimation of Pavement Structural Capacity
Authors: Romanoschi Stefan , Metcalf John B.
Published: April 2007

The use of the falling weight deflectometer (FWD) as a tool for investigating the structural strength of flexible and rigid pavements is now common. The backcalculation of layer moduli is the primary technique for data interpretation. This technique is cumbersome and expensive to apply to low-volume roads. A simple way of relating the FWD surface deflections to the performance of pavement structures, expressed by the structural number (SN), is presented. The technique is proposed as an alternative to existing methods in Louisiana using Dynaflect data. The relationship was deduced by statistical analysis, using the data collected at the Louisiana Transportation Research Center Pavement Research Facility. The study found that the correlation between the SN and the FWD deflections is satisfactory. Two different relationships are recommended for flexible and semirigid pavements. Both relationships can be applied in a pavement management environment because they allow evaluation of the required thickness for the asphalt overlay. It was found that the structural layer coefficients must be assigned functions of the laboratory moduli determined by the indirect tensile test, not functions of the backcalculated moduli.
In Situ Measurements of Secondary Road Flexible Pavement Response to Vehicular Loading
Authors: Al-Qadi Imad L. , Bhutta Salman A.
Published: April 2007

In June 1994, a secondary road pavement section 150 m long was instrumented in Bedford County, Virginia. This pavement section was composed of nine individual sections each 15 m long. Sections 1 through 3 had a limestone base course 100 mm thick (VDOT 21-B); Sections 4 through 6 had a base course 150 mm thick; and Sections 7 through 9 had a base course 200 mm thick. Three sections were stabilized with geotextiles, three were stabilized with geogrids at the base course–subgrade interface, and the other three were kept as control sections. One section from each stabilization category was included in each base course thickness group. The outside wheel path of the inner lane was instrumented with strain gauges, pressure cells, piezoelectric sensors, thermocouples, and moisture sensors. A Keithley 500-A data acquisition system was used to collect instrument responses on-site. Some of the data collected by the instruments are discussed. Section performances based on the instrumentation response to controlled and normal vehicular loading indicated that geosynthetic stabilization provided significant improvement, which was found to be in agreement with rut-depth measurements.
Management of Unpaved Road Networks on Opencast Mines
Authors: Thompson Roger J. , Visser Alex T.
Published: April 2007

In surface mining operations, ultra-heavy-haul trucks apply axle loads in excess of 200 t, but the daily load repetitions are low. Road networks for these vehicles have historically been designed empirically, relying heavily on local experience. Increasing vehicle sizes have resulted in unwarranted deformations and excessive maintenance requirements. There was thus a need to consider the transportation problem holistically, taking into account construction and maintenance costs as well as vehicle operating costs. Most opencast mines in South Africa are private endeavors, and all savings will benefit the company. A research project was undertaken in South Africa to develop a management system that takes into account different design factors. The various components of the management system are presented, and the value of its application is demonstrated through case studies. The structural design system, the pavement deterioration system, and the maintenance effectiveness are discussed. The components are then combined to provide total transportation costs and the appropriate maintenance regime to minimize total transportation cost. The system has been applied on several mines, and distinct benefits have been derived. The improved structural design of a new road resulted in a 29 percent savings in construction costs, compared with the tendered price of the empirically designed structure. In addition, improved wet weather trafficabililty was noted. Mines have also used the system as a motivation for improved maintenance equipment and strategies because significant benefits were apparent from the adoption of the maintenance management system.
Erosion Control Techniques on Forest Road Cutslopes and Fillslopes in North Alabama
Authors: Grace J. Mcfero
Published: April 2007

Road cutslopes and fillslopes account for approximately 50 percent of the total road disturbance area on steep terrain and contribute as much as 60 percent of sediment from forest roads. The significance of erosion control techniques on these vulnerable components of the road prism has become evident in recent years. A study to gain a better understanding of erosion control techniques on road cutslopes and fillslopes is detailed. Sediment and runoff yield from three erosion control treatments and a control were investigated on west-facing 2:1 and 1.5:1 cutslopes and fillslopes, respectively, on a newly constructed road during a 30-month study. The treatments evaluated were a wood excelsior erosion mat, native species grass, and exotic species grass. Factors detected to significantly affect sediment yield from road sideslopes were treatment, time, and treatment-time interaction based on analysis of variance. Significant reductions in sediment yield and runoff were found on all treatments on both the cutslope and fillslope. The erosion mat most effectively controlled erosion losses on both slopes for all study periods.
Relative Effects on a Low-Volume Road System of Landslides Resulting from Episodic Storms in Northern Idaho
Authors: Mcclelland Douglas E. , Foltz Randy B. , Falter C. Michael , Wilson W. Dale , Cundy Terrance , Schuster Robert L. , Saurbier Jim , Rabe Craig , Heinemann Ron
Published: April 2007

In late November to early December 1995 and February 1996, northern Idaho was hit by heavy rains on a deep snowpack, resulting in two flood and landslide events of historic magnitude. Each of these storms was larger than the previous significant storm, which occurred in January 1974. A study was initiated by the U.S. Department of Agriculture Forest Service to survey and study the effects of the resultant landslides on the Clearwater National Forest, including the effects on the aquatic ecosystem. The results of this study were compared with the estimated average natural sediment resulting from landslides to evaluate the incremental impacts of these recent episodic landslides. They were also compared with the results of a study conducted on the landslides resulting from the January 1974 storm to determine if the landscape was responding more severely to large storms as a result of Forest Service management activities over the past 21 years. The general results of this study indicate that, of the Forest Service management activities, roads are the major contributor; however, they contribute less sediment than natural landslides. The total resultant sediment appears to be within the transport capacity of the aquatic system, and the landslide response in 1974 was similar to the 1995–1996 response. The results of the aquatic ecosystem study were generally mixed, with some habitat parameters indicating degradation, some unchanged, and some improved as a result of the flooding or flooding with landslide sediment.
Modeling Low-Volume Road Erosion
Authors: Elliot William J. , Foltz Randy B. , Luce Charles H.
Published: April 2007

Low-volume roads are recognized as one of the primary sources of sediment in many watersheds. The authors have carried out research on the details of the complex soil erosion processes occurring on low-volume roads for more than 10 years. An overview of their research summarizes the results of numerous past and ongoing field and computer modeling studies on road erosion processes and the effects of road design on road erosion. The authors have found that insloping and outsloping effects on roads are often overshadowed by the effects of rutting. Most soil erosion on roads is from concentrated flow in ruts or ditches. Adding gravel increases hydraulic conductivity and reduces erosion. Road erosion rates can also be decreased by reducing tire pressure or by removing roads. The authors are developing applications of the Water Erosion Prediction Project model as user-friendly erosion prediction tools for road managers. Further work is required to quantify the effects of current management techniques on water quality and to develop new low-impact road design and management technology.
Modeling Erosion from Insloping Low-Volume Roads with WEPP Watershed Model
Authors: Tysdal Laurie M. , Elliot William J. , Luce Charles H. , Black Thomas A.
Published: April 2007

Low-volume roads can be a major source of sediment to streams in forest watersheds. For soil erosion from roads to be economically mitigated, the processes that cause erosion need to be understood. The Water Erosion Prediction Project (WEPP), a physically based erosion and sedimentation model, was used for predicting erosion from forest roads that can be described as hillslopes. Watershed applications of WEPP predicted erosion and sedimentation values for insloping roads that can be described as microwatersheds. How well WEPP models insloping roads through a sensitivity analysis and validation process using two studies in the Oregon Coast Range is discussed.
Truck Delay and Traffic Conflicts Around Weigh Stations: A Case Study in Illinois
Authors: Benekohal Rahim F. , El-Zohairy Yoassry M. , Forrler Earl , Aycin Murat F.
Published: April 2007

Truck weight enforcement helps protect infrastructure and improve traffic safety. However, requiring all trucks to stop at all weigh stations reduces productivity and increases enforcement costs. This pilot study was conducted at the Williamsville weigh station in Springfield, Ill., to quantify the delay and traffic conflicts experienced by trucks around weigh stations. The quantification is needed to evaluate the effectiveness of automatic vehicle identification/weigh in motion (AVI/WIM) systems for electronic screening of trucks at weigh stations. The main emphasis of this project is to examine potential benefits of intelligent transportation system (ITS) technologies for intrastate commercial vehicle operations (CVO) applications. Reducing the number of traffic conflict incidents due to the merging and diverging movements of trucks would increase traffic safety. In the case study, without the AVI/WIM system, on the average, 30 percent of all trucks could not be weighed because the weigh station was temporarily closed to prevent a queue backup. The average delay was 4.95 min/truck and varied from 3.56 to 6.59 min/truck. The maximum delay varied from 8.69 to 137.62 min/truck. There were significant numbers of conflicts even under light-volume conditions. Models to predict the number of conflicts were developed. The number of diverge conflicts depends on car and truck volumes, and the number of merge conflicts depends on the truck volume on the ramp and the car volume in the right and middle lanes of a six-lane interstate.
Methodology for Evaluating Large Truck Access to Intermodal and Other Facilities
Authors: Aultman-Hall Lisa , Hill Michael L. , Agent Ken
Published: April 2007

In a recent project for the Kentucky Transportation Cabinet (KYTC), researchers were tasked with developing a method to evaluate objectively the access for large trucks between intermodal or other truck-traffic-generating sites and the National Highway System (NHS). The routes evaluated were the actual roadway segments used by trucks traveling between intermodal or other facilities and the NHS. The choice to evaluate specific heavily used roadway segments, as opposed to evaluating an entire highway or roadway corridor, was based on the recommendation of Kentucky’s Intermodal Advisory Panel, which advises the KYTC on intermodal issues. This allowed researchers to identify the actual problems being experienced, even when the routes included segments of many different highways and jurisdictions. Part of this study included the development of objective measures that could be used for comparing and prioritizing sections. The methodology that was developed and is currently being used to evaluate routes to 50 truck-trip generators throughout Kentucky is documented. The procedure begins with a telephone survey of site operators/managers to identify route problems. Each route is evaluated with respect to three types of features: subjective, point, and continuous. The ranking of each point and continuous element as “preferred,” “adequate,” or “less than adequate” is converted to a relative urgency rating by assigning relative weights for truck volume and section length. Point and subjective features are identified for spot improvements when appropriate. Finally, the overall route is graded on a subjective scale of 1 to 10.