bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of an Adaptive Control Strategy in a Live Intersection Laboratory
Authors: Kwon Eil , Stephanedes Yorgos J.
Published: April 2007

The current status of the Minnesota intersection laboratory and a new adaptive control strategy developed using the laboratory environment are presented in this paper. The laboratory is equipped with a machine-vision detection system with 6 cameras that are collecting detailed traffic data from a total of 110 virtual detectors. The new control method is based on the link-congestion index that quantifies the link-wide level of congestion, using the point measurements from traffic sensors (e.g., machine-vision detectors or conventional loops). Further, using the data collected from the laboratory, a new microscopic simulator was also developed to meet the specific needs for the laboratory environment. The current version of the simulator adopts a modified cellular automata approach with the simplified car-following model, which was developed and tested in this work. The evaluation results with the simulator indicated significant performance improvements of the new strategy over the pretimed and the current actuated-control strategies being operated in Minneapolis. Currently the control method is being refined for field evaluation at the intersection laboratory.
Evaluating Median Crossover Likelihoods with Clustered Accident Counts: An Empirical Inquiry Using the Random Effects Negative Binomial Model
Authors: Shankar Venkataraman N. , Albin Richard B. , Milton John C. , Mannering Fred L.
Published: April 2007

Insights into plausible methodological frameworks specifically with respect to two key issues—(1) mathematical formulation of the underlying process affecting median crossover accidents and (2) the factors affecting median crossover frequencies in Washington State—are provided in this study. Random effects negative binomial (RENB) and the cross-sectional negative binomial (NB) models are examined. The specification comparisons indicate benefits from using the RENB model only when spatial and temporal effects are totally unobserved. When spatial and temporal effects are explicitly included, the NB model is statistically adequate, while the RENB model appears to lose its distributional advantage. Such findings might be artifacts of the median crossover accident dataset used in this study. While the NB model appears to be the superior model in the present case of median crossover accidents, the marginally inferior performance of the RENB model warrants further examination through application to regular accident types in light of its flexibility to incorporate temporal and cross-sectional variations simultaneously in panel counts. From a predictive standpoint, RENB offers advantages in terms of model transferability and updating.
Adult Learning Styles and Effective Transfer of Information
Authors: Divine Deborah Reaves
Published: April 2007

Effective training and other technology transfer (T2) activities occur when teachers/trainers or T2 agents recognize and use training techniques that correspond to the learning styles of their learner audiences. Learning style is defined as one’s personally preferred way of processing information and experience. It crosses all content areas. It is affected by both intrinsic and extrinsic factors such as stress, world view, and environment. Each learner has the ability to utilize a variety of learning styles, and each teacher has a preferred teaching style based on his or her preferred information processing mode. Each learner learns most comfortably and fastest when his or her preferred learning style meshes with the teaching style of the teacher/trainer. Often teacher/trainers do not have the time, funds, or opportunity to determine their learners’ preferred styles. The effective teacher/trainer utilizes a variety of teaching techniques to engage and convey the most information to the most learners.
Effect of Film Thickness on the Rheological Properties of Asphalts in Contact with Aggregate Surface
Authors: Huang Shin-Che , Branthaver Jan F. , Robertson Raymond E. , Kim Sang-Soo
Published: April 2007

The effect of the interaction between aggregate and asphalt on asphalt mix properties has been a subject of many studies. However, studies using compacted mixtures cannot isolate the pure effects of the asphalt-aggregate interactions, while studies using mixtures of asphalt and fines cannot determine the asphalt rheology at the interface. In this study, direct measurement of asphalt rheology at the interface is investigated using the sliding plate geometry with machined aggregate plates. Significant differences in the behavior of asphalts in contact with aggregate plates have been observed, especially at low shear rates. One asphalt shows substantial aggregate surface-induced structuring, while another asphalt shows essentially none. In addition, the film thickness effect on the rheological properties of asphalt binders and asphalt aggregate mixtures was investigated. The results strongly show that thin films of asphalt on an aggregate surface have substantially changed rheological properties that are asphalt composition–dependent, and that asphalts that are graded alike as bulk materials do not have the same rheological properties as thin films, in this service environment.
Development of a Modified Rotavapor Apparatus and Method for Short-Term Aging of Modified Asphalts
Authors: Sirin Okan , Shih Chuang-Tsair , Tia Mang , Ruth Byron E.
Published: April 2007

An alternative laboratory asphalt aging process that could be used to simulate the aging effects of hot mixing on modified asphalts was developed and evaluated. The rotavapor apparatus, which has been used for recovery of asphalt from solution, was modified to work as an aging device for asphalts and modified asphalts. The rotavapor apparatus was modified such that the vacuum connection was replaced by an air pump with a controlled air flow. To reduce the variation of aging condition due to variation of the temperatures in the oil bath of the rotavapor apparatus, an insulated covering for the oil bath was constructed and used in this aging process. Evaluation results indicate that the aging severity of the modified rotavapor aging process is affected by variables such as process temperature, duration, and sample weight. All these factors could be adjusted to achieve the desirable level of asphalt aging. Because of the flexibility in controlling these variables in the modified rotavapor process, it appears that this method could be used to simulate the aging effects of hot mix plant process effectively.
Performance Characteristics of Asphalt Binders and Mixtures Modified by Waste Toner
Authors: Solaimanian Mansour , Kennedy Thomas W. , Tripathi Rakesh
Published: April 2007

Every year, a tremendous amount of toner is produced for copiers and printers by toner manufacturing companies throughout the United States. Some of this toner does not meet quality specifications and becomes a waste of the manufacturing process. This waste and the spent toner from copiers and printer cartridges are dumped in landfills for lack of a better way of utilizing them. A cooperative research project was undertaken by Texas Department of Transportation and the University of Texas to investigate the feasibility and potential benefits of utilizing waste toner in hot mix asphalt concrete. The research program included procurement of a number of different waste toners, blending them with asphalt cement at different ratios, and evaluating binder and mixture properties. The results indicated that as the amount of waste toner in the blend increases, the stiffness and viscosity of the modified binder increase. The mixture analysis also indicates higher strength and stability for toner-modified asphalt concrete compared with unmodified mixtures. The toner-modified binder is expected to perform satisfactorily in areas where permanent deformation is of great concern and some increase in low-temperature stiffness is not regarded as posing any cracking problems. It was found that a PG64-28 asphalt will grade as PG70-22 with the addition of 10 percent waste toner.
Effect of Allowable Thickness Variation on Backcalculated Moduli
Authors: Jooste Fritz , Kekwick Stephen V. , Muthen Marshal
Published: April 2007

The effect of small variations in pavement layer thicknesses on the accuracy of backcalculated moduli was investigated. Deflection data were generated using simulated pavement structures in which layer thicknesses were varied by small amounts. This variation in layer thicknesses was kept sufficiently small so that all layers would conform to construction specifications. A backcalculation was then performed on the generated deflection data. Only the average design thicknesses were supplied to the backcalculation software. Errors between backcalculated moduli and those moduli that were used to generate the deflection data were then studied. It was found that even small variations in layer thicknesses influenced the accuracy of the backcalculated moduli to a significant extent. Where the subgrade depth was considered to be variable, the backcalculation error due to small variations in layer thicknesses was at least 5 percent. For the pavement structures studied, the subbase layer proved to be most sensitive to layer thickness variations. The subgrade appeared to be least sensitive to small variations in layer thicknesses. Thin, stiff layers such as a stabilized subbase were found to be most sensitive of all to layer thickness fluctuations. Despite the large variations in backcalculated moduli at individual data points, the average backcalculated moduli for the entire data set of each pavement structure compared well with the correct modulus value (i.e, the modulus values used to generate the deflection data).
Crash Experience on Tined and Continuously Ground Portland Cement Concrete Pavements
Authors: Drakopoulos Aris , Wenzel Thomas H. , Shober Stephen F. , Schmiedlin Robert B.
Published: April 2007

Crash rates were compared between 290 km of continuously ground and 115 km of transversely tined portland cement concrete pavements in Wisconsin. All 11,219 reported crashes at the study sites during the 6-year period 1988 through 1993 were analyzed. Continuously ground surfaces were found to have lower crash rates than tined surfaces under dry and wet conditions during daytime and nighttime as well as under all four combinations of pavement and light conditions. Ground pavements had 58 percent the crash rates of tined pavements under dry and wet conditions; the ratio was 84 percent when snow or ice was present on the pavement; however, relatively limited vehicular travel occurred under such conditions and these results are viewed as preliminary. Ground pavements had 57 percent the crash rates of tined pavements during daytime; the ratio was 73 percent at night. On the basis of the available data, a hypothesis of increasing crash rates with time (based on frictional property deterioration with pavement age, cumulative vehicle passes since construction, or both) could not be confirmed for either type of pavement texture.
Optimization Approach to Highway Safety Improvement Programming
Authors: Pal Raktim , Sinha Kumares C.
Published: April 2007

A procedure is developed for optimal allocation of highway safety improvement funds. The approach minimizes the total number of crashes in a study area during an analysis period within the constraints of funding resources. The uniqueness of the model lies in its flexibility for considering the effectiveness of safety improvement projects in future years. The model can consider carryover of unspent funds from previous years. The effect of errors involved in estimation of initial investment costs, annual maintenance costs, crash reduction rates, and additional traffic growth factors can be studied. The application of the model is illustrated. The effect of funding level on the effectiveness of the safety improvement program is studied through sensitivity analysis.
Impact of 65-mph Speed Limit on Iowa’s Rural Interstate Highways: Integrated Bayesian Forecasting and Dynamic Modeling Approach
Authors: Raju Shanmuganathan , Souleyrette Reginald , Maze Thomas H.
Published: April 2007

In 1987, a provision of the Surface Transportation and Uniform Relocation Assistance Act allowed states to raise speed limits on rural Interstates to 65 mph (104.6 km/h). By 1995, nearly all states had done so. Several studies have investigated the safety impacts of these increases. Methodologies varied from analysis of variance to simple before and after comparison and have included time series procedures, with and without intervention variables. In general, these studies have produced contradictory findings. An integrated Bayesian forecasting and dynamic modeling approach used to determine the impact of the increased speed limit on rural Interstates of Iowa is reported. The approach is used to verify that raising the speed limit to 65 mph (104.6 km/h) led to an increase in fatal accidents on rural Interstates of Iowa. Comparison of fatal accident data on rural Interstates of Iowa and New Jersey yields similar results. Although this conclusion was anticipated, the study further demonstrates that a Bayesian/dynamic approach is more robust than the standard time series model.
Engineering Application of Washington State’s Pavement Management System
Authors: Baker Michael J. , Mahoney Joe P. , “Siva” Sivaneswaran Nadarajah
Published: April 2007

Previous investigation into the Washington State Department of Transportation’s (WSDOT) Pavement Management System (WSPMS) revealed pavement sections on the state route system that were outperforming or underperforming other pavement sections constructed of similar materials and subjected to similar traffic and environmental conditions. Reasons were not clear. The WSPMS was used to identify superior and inferior candidate pavements for further investigation. All state route pavements were stratified into 18 distinct analysis groups, and population statistics were generated for each group providing WSDOT with a snapshot of the current “state of the state route system” and providing the basis for selecting candidate pavements. The five performance measures considered included: age of the surface course, a distress-based pavement structural condition score, annual design-lane equivalent single axle loads, roughness (in terms of International Roughness Index), and rutting. Results of the analysis suggest that WSDOT is properly designing layer thicknesses at appropriate reliability levels. Also, in 6 of 10 analysis group comparisons, inferior pavements were actually thicker than superior pavements. Both findings suggest that thickness design factors are not the primary cause of inferior performance in Washington State; construction, material and site specific factors are likely the cause. Additionally, in an international effort to exchange information on pavement performance and construction practices, highlights of a comparative study of pavement performance with South Africa’s Gauteng Department of Transportation are presented.
Project Scoping Using Falling Weight Deflectometer Testing: New Jersey Experience
Authors: Zaghloul Sameh , He Zhiwei , Vitillo Nick , Brian Kerr J.
Published: April 2007

The experience of New Jersey with pavements, like that of many other states, goes back to the last century. Highways constructed early in this century are still in service. During these extensive service lives, several maintenance and rehabilitation activities were applied to keep the pavements in good condition. These activities ranged from patching to full reconstruction. Also, most of New Jersey pavements have been widened at least once. With all these factors, it is difficult to identify the limits of homogeneous sections that should receive the same rehabilitation treatment. In 1996, the New Jersey Department of Transportation started a limited network level falling weight deflectometer (FWD) program. This program has short- and long-term goals. The short-term goals include identifying the limits of homogeneous sections (sectionalization), assessing the pavement structural capacity, estimating the remaining service life, and determining the future rehabilitation needs. The long-term goal of the project is to use the FWD measurements for the ongoing development and refinement of the models used to predict remaining structural life for use in economic evaluation models. The procedure followed to achieve the short-term goals of the project and an outline of the findings of the project are summarized.
Vehicle Re-Identification and Travel Time Measurement in Real-Time on Freeways Using Existing Loop Detector Infrastructure
Authors: Coifman Benjamin
Published: April 2007

A new vehicle re-identification algorithm for two consecutive detector stations on a freeway, whereby a vehicle measurement made at the downstream detector station is matched with the vehicle’s corresponding measurement at the upstream station, is presented in this paper. The method is illustrated using effective vehicle length measured at dual-loop speed traps, but it is transferable to other detectors capable of extracting a vehicle signature (such as video image processing). This approach is significant because no one has attempted to use the existing detector infrastructure to match vehicle measurements between detector stations. The algorithm should improve freeway surveillance via travel time measurement, which is simply the difference between the known arrival times at the two stations for a matched vehicle. The re-identification algorithm is tolerant to noise; instead of finding the ‘best match’ for each vehicle, it finds all possible matches and then looks for sequences of vehicles from the possible matches. Even with noisy loop detector data, the sequence detection eliminates most of the possible-but-incorrect matches while the true matches remain. The new methodology will be used to examine the applications and benefits of travel-time data on real-world traffic, without the expensive costs of installing new detectors. Ordinarily, a travel-time measurement system would have to be fully deployed before the benefits can be quantified.
Integration of Dynamic Traffic Assignment with Real-Time Traffic Adaptive Control System
Authors: Gartner Nathan H. , Stamatiadis Chronis
Published: April 2007

Intelligent transportation systems (ITS) are being designed to provide real-time control and route guidance to motorists to optimize traffic network performance. Current research and development efforts consist of a dynamic traffic assignment capability that can predict future traffic conditions and a real-time traffic adaptive control system (RT-TRACS) for generation of signal control strategies. Although these models are intimately connected, so far they have developed independently of one another. A framework is presented here for integrating the two models into a combined system with a practical approach for realizing it. First the static case involving the interaction between travelers (demand) and transportation facilities (supply) under recurrent conditions is discussed. This model is applicable in the design and planning of transportation systems management actions. The framework is then extended to the quasi-dynamic and the dynamic cases, which involve incorporation of advanced ITS technologies in the form of advanced traffic management systems and advanced traveler information systems. An innovative application of this framework to advanced traffic-adaptive signal control is presented using the hierarchic structure of RT-TRACS.
One-Dimensional and Two-Dimensional Estimates of Abutment Scour Prediction Variables
Authors: Sturm Terry W. , Chrisochoides Antonis
Published: April 2007

An experimental study of the estimation of hydraulic parameters needed in bridge abutment scour formulas is presented. Two different compound channel geometries are studied with rough floodplains in shallow overbank flow. Vertical-wall and spill-through abutment shapes are included in the study, with the abutment face located on the floodplain for various embankment lengths. Water surface profiles and velocity distributions are measured and compared with predictions made by the one-dimensional (1-D) model WSPRO and a two-dimensional k-ε turbulence model developed in previous research. The results show that a 1-D model can predict scour parameters reasonably well in the bridge approach section but not in the bridge contraction section.
NCHRP Report 350 Compliance Testing of the Beam-Eating Steel Terminal System
Authors: Pfeifer Brian G. , Sicking Dean L.
Published: April 2007

An energy-absorbing guardrail terminal was developed at the Midwest Roadside Safety Facility in 1994 that met the safety criteria set forth in NCHRP Report 230. This terminal, known as the beam-eating steel terminal, or BEST, relies on the cutting of steel W-beams to absorb the energy of impacting vehicles. Since that time, a new set of safety standards has been developed to replace those set forth in NCHRP Report 230. These new criteria are published in NCHRP Report 350, with the most significant change being the replacement of the 2041-kg (4,500-lb) sedan test vehicle with a 2000-kg (0.75-ton) pickup. To ensure that the BEST system would perform well under these new, and more stringent, criteria, the system was subjected to the matrix of full-scale vehicle crash tests required by NCHRP Report 350. Several design changes were made to the terminal system during this development to improve the performance of the system. The results of this successful program are reported.
Finite-Element Modeling of Guardrail Timber Posts and the Post-Soil Interaction
Authors: Plaxico Chuck A. , Patzner Gregory S. , Ray Malcolm H.
Published: April 2007

The performance of many guardrail terminal systems is dependent on the strength of timber guardrail posts and soil conditions. Accurately simulating the breakaway characteristits of guardrail posts mounted in soils is an important issue concerning researchers in the roadside safety community. Finite-element analysis is one method that can be used to evaluate roadside hardware designs, but good simulations are contingent on developing accurate models of the components. A description is provided of the development of a model of a breakaway timber post and soil system used in the breakaway cable terminal (BCT) and the modified eccentric loader terminal (MELT). The model is described and simulation results are compared with data from physical tests of BCT/MELT posts.
Using STEAM for Benefit-Cost Analysis of Transportation Alternatives
Authors: Decorla-Souza Patrick , Cohen Harry , Haling Dan , Hunt James
Published: April 2007

The Intermodal Surface Transportation Efficiency Act emphasizes assessment of multimodal alternatives and demand management strategies. This emphasis has increased the need for planners to provide good comparative information to decision makers with regard to proposed alternative transportation solutions. Benefit-cost analysis is a useful tool to compare the economic worth of alternatives and evaluate tradeoffs between economic benefits and nonmonetizable social and environmental impacts. FHWA has developed a new tool for benefit-cost analysis called the Surface Transportation Efficiency Analysis Model (STEAM). The software is based on the principles of economic analysis and allows development of monetized impact estimates for a wide range of transportation investments and policies, including major capital projects, pricing, and travel demand management. Impact measures are monetized to the extent feasible, and quantitative estimates of natural resource usage (e.g., energy consumption) and environmental impact (e.g., pollutant emissions) are also provided. Decision makers can then use net monetary benefits (or costs) of alternatives as computed by STEAM to evaluate tradeoffs against nonmonetizable impacts. The software was applied in evaluation of corridor alternatives for the Central Freeway corridor in the hypothetical urban area of Any City, U.S.A.
ROADVEG: Utah Department of Transportation Roadside Vegetation Inventory and Geographic Information System
Authors: Bickford Ira , Curto Michael , Glazier Chris , Macmahon James A.
Published: April 2007

The Utah Department of Transportation (UDOT), in collaboration with the Utah State University Ecology Center, has created a geographic information system (GIS) of spatially referenced roadside and context landscape attributes pertinent to roadside vegetation management. Construction of the ROADVEG GIS involved the design of a relational database, the assignment of attributes to 2200 km (1,365 mi) of road segments through on-the-road field inventories, and the linkage of database attributes to spatial coverages for GIS presentation and query. The ROADVEG GIS offers UDOT personnel a new way to remotely assess existing roadside and context vegetation attributes along Utah’s roadways, as well as a potentially powerful method of performing multivariate spatial queries for long-range planning. Through queries of the ROADVEG inventory, road segments with specified multivariate conditions are readily identifiable. Visual depictions of multiple vegetation management scenarios with varying cost-benefit ratios are now possible.
Work Zone Traffic Accidents Involving Traffic Control Devices, Safety Features, and Construction Operations
Authors: Bryden James E. , Andrew Laurel B. , Fortuniewicz Jan S.
Published: April 2007

There were 496 work zone traffic accidents on New York State Department of Transportation construction projects from 1994 through 1996. These accidents involved impacts with work zone traffic control devices and safety features; construction features, such as pavement bumps and joints; drainage features; excavations and materials; and construction vehicles, equipment, and workers. These items, which include all of the features introduced into the roadway environment by construction activity, represent one-third of all work zone accidents and 37 percent of those involving serious injury. Channelizing devices, arrow panels, signs, and other traffic control devices generally resulted in little harm when impacted. Impact attenuators, both fixed and truck mounted, also performed well. Although portable concrete barriers prevent vehicle intrusions, impacts with barrier are severe events. Barriers must be properly designed and limited to only those locations where they are needed to protect more serious hazards. Construction vehicles, equipment, and workers were involved in over 20 percent of all work zone accidents, resulting in serious injuries. Although intrusions by private vehicles into work spaces are a serious concern, construction vehicles, equipment, and workers in open travel lanes are also a serious concern. Good design of work zone traffic control plans, combined with adequate training and supervision of workers, is essential to control both concerns.
Regional Intelligent Transportation Systems Architectures and the Competitive Region
Authors: Rodríguez Daniel A. , Muñoz-Loustaunau Abel , Pendleton Todd , Sussman Joseph M.
Published: April 2007

The role of an architecture for deploying intelligent transportation systems in finding solutions to regional transportation problems is analyzed. The concept of a competitive region, a region with changing economic interests, stakeholders, and borders, is reviewed. The competitive region motivates finding solutions to transportation problems of regional scope. The concept of a regional system architecture is then introduced as a catalyst for reaching coordinated regional solutions. The regional architecture’s flexibility and ability to bring different stakeholders together make it an ideal tool for planning for intelligent transportation systems deployment in the competitive region while strengthening the traditional transportation planning process. The province of Mendoza, Argentina, is presented as a research case study for using an architecture for shaping a regional transportation system. The research shows that the fundamental issues to address in ITS deployment are institutional in nature and that a system architecture can become a strategic tool for developing transportation improvements in the context of regional coordination.
Knowledge Acquisition for Large-Scale Expert Systems in Transportation
Authors: Adler Jeffrey L. , Persaud Eknauth
Published: April 2007

One of the greatest challenges in building an expert system is obtaining, representing, and programming the knowledge base. As the size and scope of the problem domain increases, knowledge acquisition and knowledge engineering become more challenging. Methods for knowledge acquisition and engineering for large-scale projects are investigated in this paper. The objective is to provide new insights as to how knowledge engineers play a role in defining the scope and purpose of expert systems and how traditional knowledge acquisition and engineering methods might be recast in cases where the expert system is a component within a larger scale client-server application targeting multiple users.
Why We Should Develop a Truly Automated Highway System
Authors: Shladover Steven E.
Published: April 2007

The reasons in favor of developing an automated highway system (AHS) are addressed. The anticipated benefits in highway capacity increases, travel time reductions, safety improvements, reduction of driving stress and tedium, elimination of adverse driving behavior, alternative uses of traveling time, more predictable travel time, and reduction of exhaust emissions and energy consumption are reviewed. The concerns that have been raised by those who are skeptical of AHS are then reviewed, indicating which have already been addressed and which remain subject to continuing uncertainty and research.
Microscopic Simulation Analysis for Automated Highway System Merging Process
Authors: Ran Bin , Leight Shawn , Chang Ben
Published: April 2007

The automated highway system (AHS) concept with dedicated lanes is not designed as a stand-alone transportation facility. Drivers will by necessity need to drive from their origins to the AHS entrance and from the AHS exit to their final destinations. Therefore, the AHS will affect other transportation facilities and will need to be integrated with all other facilities in the transportation system. Interfaces create much of the congestion for today’s transportation systems. AHS interfaces may cause similar problems, as a result of either AHS interactions with conventional systems or internal limitations from AHS merging capabilities. If these problems exist, either the AHS or the conventional road network cannot function properly. Then the system as a whole will break down, and the AHS could prove a detriment to the overall transportation system. Clearly not enough is known about the automated merging process to determine what conditions would lead to congestion at interface points. Current macroscopic techniques assume parameters that are not applicable to an AHS, and no detailed AHS merging models have been developed and validated. The AHS to conventional roadway interface problem is addressed by presenting a microscopic simulation model for one scenario of the automated merging maneuver. Some numerical results are presented for this merging scenario.
Evolving Interoperability with National Transportation Communication for Intelligent Transportation Systems Protocols
Authors: Seymour Edward J. , Patel Raman K.
Published: April 2007

One of the most exciting developments in the intelligent transportation systems (ITS) industry—one that holds so much promise for the future—is the National Transportation Communications for ITS Protocols (NTCIP). NTCIP will help lead the way to achieve a cost-effective deployment and management of ITS applications. It will also influence the design and manufacturing process and should cause changes in the way system integrators do their work. The resulting interoperability of core functionality between transportation devices will be an enabling service for ITS deployment. Developmental efforts, the implications of NTCIP, and the resulting interoperability for transportation applications are reported. The framework of the NTCIP is described and device level interoperability is discussed. NTCIP makes an effort to fulfill the initial needs for interoperable and interchangeable field devices. Current developments of the NTCIP effort are described and interoperability features are identified.
Westergaard Curling Solution Reconsidered
Authors: Ioannides Anastasios M. , Davis Craig M. , Weber Christopher M.
Published: April 2007

An in-depth and systematic examination is presented of the effect of temperature gradients on slab-on-grade pavements. The main objective for the examination was the development of practical design tools for use in a typical engineering office. This has been achieved by a critical reconsideration of the literature, a synthesis of currently available analytical resources, and the implementation of recent technological achievements promulgated in related areas of engineering. Prominent among these are the application of the principles of dimensional analysis, the finite element method, advanced statistical regression analysis, and artificial neural networks (ANN). A number of ANNs have been trained for the curling problem, and in several instances they are found to be more efficient predictive tools than corresponding statistical regression equations. It is found that the most important shortcomings of the Westergaard curling solution are the assumption of continuous contact between slab and subgrade (infinite slab self-weight) and the explicit treatment of only daytime conditions. Although Westergaard’s curling-only predictions are significantly inferior to those from ANN and statistics, his load-plus-curling predictions exhibit approximately the same scatter as those from these two more modern and nominally more sophisticated tools. The case of Westergaard’s curling solution can serve as an example pointing to the usefulness and desirability of theoretical solutions, even when these are achievable only on the basis of considerable abstraction and simplification.
Thin Conductive Concrete Overlay for Bridge Deck Deicing and Anti-Icing
Authors: Yehia Sherif A. , Tuan Christopher Y.
Published: April 2007

Concrete bridge decks are prone to ice accumulation. Bridge decks freeze before the roads approaching them freeze, making wintry highway travel treacherous. Road salts and deicing chemicals are effective for ice removal but cause damage to concrete and corrosion of reinforcing steel in concrete bridge decks. The resulting rapid degradation of existing concrete pavements and bridge decks is a major concern to transportation and public-works officials. The use of insulation materials for ice control and electric or thermal heating for deicing have been attempted, with unsatisfactory results. Conductive concrete is a cementitious admixture containing electrically conductive components to attain high and stable electrical conductivity. Due to its electrical resistance and impedance, a thin conductive concrete overlay can generate enough heat to prevent ice formation on a bridge deck when connected to a power source. In 1998, Yehia and Tuan, at the University of Nebraska–Lincoln, developed a conductive concrete mix specifically for bridge deck deicing. In this application, a conductive concrete overlay is cast on the top of a bridge deck for deicing or anti-icing. The mechanical and physical properties of the conductive concrete mix after 28 days have met ASTM and AASHTO specifications. Two concrete slabs were constructed with a 9-cm (3.5-in.) conductive concrete overlay for conducting deicing experiments in the natural environment. Deicing and anti-icing experiments were conducted in five 1998 snowstorms. Average power of about 590 W/m2 (55 W/ft2) was generated by the conductive concrete overlays to prevent snow and ice accumulation.
Road/Weather Information System Architecture for Integration and Expansion
Authors: Kwon Taek Mu , Fleege Edward
Published: April 2007

Because of rapidly changing technologies and associated increasing costs, implementation of a Road/Weather Information System must be carefully planned. Planners know the importance of starting with an architecture that allows easy integration of new and legacy technologies and easy expansion to a larger system. A layered, hierarchical architecture is proposed to meet that objective. A prototype of this model was implemented in the Minnesota Department of Transportation District 1. This system is described in brief.
Tailoring a National Winter Maintenance Policy for a Region: A Case from the Häme Region in Finland
Authors: Raukola Tapio J. , Grekula Janne , Martikainen Päivi
Published: April 2007

National policies are a necessary framework for uniform road management within a country. Regional road management often requires more precise guidelines to account for local conditions. Only nationwide road management policies have been implemented in Finland. In 1999, the Häme region of Finland targeted sites for improving winter maintenance for short sections of road because of local conditions or temporary traffic needs. The new guidelines will be used as a maintenance contract document. Main and secondary roads were included in developing the regionally tailored policy in the Häme region. The use of targeted winter maintenance sites increases costs by about 4.5 percent, while improving winter service to road users. What is new in targeted winter maintenance? Obviously the biggest difference between the old and new practices, or the nationwide and regional policies, is the systematic approach. All road maintenance needs have been analyzed, and the targeted sites have been selected after comprehensive analysis. The workload and costs have been calculated, and the selected sites can be used in contract negotiations.
New Stopping Sight Distance Model for Use in Highway Geometric Design
Authors: Fambro Daniel B. , Fitzpatrick Kay , Koppa Rodger J.
Published: April 2007

Stopping sight distance is an important design parameter in that it defines the minimum sight distance that must be provided at all points along the highway. Thus, it influences geometric design values, construction costs, and highway safety. Stopping sight distance is defined as the sum of two components—brake reaction distance and braking distance. The basic model for calculating stopping sight distances was formalized in 1940, and the model’s parameters have been altered to compensate for changes in eye height, object height, and driver behavior over the past 50 years. Recent studies, however, question whether the model’s parameters and assumptions represent real-world conditions. A new model for determining stopping sight distance requirements for geometric design of highways is presented. This model is based on parameters describing driver and vehicle capabilities that can be validated with field data and defended as safe driving behavior. More than 50 drivers, 3,000 braking maneuvers, 1,000 driver eye heights, and 1,000 accident narratives were used to develop the recommended parameter values for the new model. The recommended values are attainable by most drivers, vehicles, and roadways. This model results in stopping sight distances, sag vertical curve lengths, and lateral clearances that are between the current minimum and desirable requirements and crest vertical curve lengths that are shorter than current minimum requirements.
Sight Distance for Stop-Controlled Intersections Based on Gap Acceptance
Authors: Harwood Douglas W. , Mason John M. , Brydia Robert E.
Published: April 2007

The current AASHTO policy for sight distance at Stop-controlled intersections is based on a model of the acceleration performance of a minor-road vehicle turning left or right onto a major road and the deceleration performance of the following major road vehicle. An alternative intersection sight distance model based on gap acceptance is developed and quantified. Field studies that were performed to determine the critical gaps appropriate for use in sight distance design are described. It is recommended that the sight distance along the major road for a passenger car at a Stop-controlled intersection should be based on a distance equal to 7.5 s of travel time at the design speed of the major road. Longer sight distances are recommended for minor-road approaches that have sufficient truck volumes to warrant consideration of a truck as the design vehicle.
Evaluation of the Passing Process on Two-Lane Rural Highways
Authors: Polus Abishai , Livneh Moshe , Frischer Benyamin
Published: April 2007

The main purpose of this research was to develop models to quantify the major components of the passing process. A second goal was to compare the results with existing highway-design models and to arrive at conclusions about the applicability of the existing models. Additional objectives were to evaluate several time elements of the passing process, such as the response time of drivers from the arrival of a proper gap until the start of the passing maneuver. The evaluation is based on an analysis of data that were collected by videotaping six tangent two-lane highway sections from high vantage points and from a helicopter hovering above one site. Normal driver behavior was not disturbed during the data collection process. About 1,500 passings were recorded; of these, 54 percent were characterized as “single passing,” in which one driver passed a single, slower vehicle. About half of all passing maneuvers were found to involve two cars; in the other half, at least one truck was overtaken. A model showing the relationship between the speed of the impeding vehicle and the passing distance was calibrated, and the implications for highway-design procedures were discussed. Several of the findings had unique safety implications, such as the very short headway before the start of the passing maneuver and very short driver-reaction times. The primary results of the analyses enabled determination of the required passing distances and, therefore, the sight distances needed for different design speeds and various traffic combinations. Additional safety-related aspects are evaluated and discussed.
Influence of Experimental Pavement Markings on Urban Freeway Exit-Ramp Traffic Speeds
Authors: Retting Richard A. , McGee Hugh W. , Farmer Charles M.
Published: April 2007

Motor vehicle crashes on curved roadway sections occur more frequently and tend to be more severe than those on straight sections. Speed is a significant factor in many crashes that occur on curves. The effects on traffic speeds of special pavement markings intended to reduce speeds on freeway exit ramps with horizontal curves were examined. An experimental pavement marking pattern was employed that narrowed the lane width of both the curve and a portion of the tangent section leading into the curve by use of a gradual inward taper of existing edgeline or exit gore pavement markings or both. Traffic speeds were analyzed before and after installation of the pavement markings at four experimental ramps in New York and Virginia. Results indicated that the markings were generally effective in reducing speeds of passenger vehicles and large trucks. The markings were associated with significant reductions in the percentages of passenger vehicles and large trucks exceeding posted exit-ramp advisory speeds.
Testing for the Significance of Induced Highway Travel Demand in Metropolitan Areas
Authors: Barr Lawrence C.
Published: April 2007

A research study was conducted to evaluate and quantify the effect of highway capacity improvements on travel demand. Statistical models using Nationwide Personal Transportation Survey data were designed to estimate relationships between average household travel time and vehicle-miles of travel. Several regression models were estimated, and the results were stratified by urbanized area, public transportation availability, metropolitan area size, family life cycle, day-of-week of travel, and population density. Travel-time elasticities of -0.3 to -0.5 were generally found, after taking into account the effects of household size, income, population density, and household employment. These results suggest that travelers will spend 30 to 50 percent of the time savings afforded by highway improvements in additional travel. Overall, the results of this study provide evidence that highway capacity improvements can create additional travel, although the magnitude of the induced traffic effect was found to be smaller than that reported by some previous researchers.
Traffic Forecasting as if Intersection Control Matters: The Sequel
Authors: Granato Sam
Published: April 2007

For the second time within 5 years, the traffic forecasting model application developed by the planning staff for the Cedar Rapids, Iowa, area metropolitan planning organization (MPO) has achieved not only a base-year accuracy that exceeds what other, larger MPOs have accomplished, but also a travel-volume and travel-time accuracy for the relatively high-volume streets that, in most cases, is not significantly different from the sampling error of field observations. Comparable success has also been achieved in modeling peak-hour traffic patterns, where applications have also been developed to model peak-hour factoring and design hour volumes for transportation projects. The standard of accuracy that has been achieved for this metro area has been made possible by two major differences from typical MPO practice. First, travel estimates (trip generation rates) are based on field-measured vehicle-trip rates rather than the common practice of a stated-response travel survey of the public (i.e., on what people do rather than what they say they do). Second, and far more important, the modeling is based on the dynamic integration of the Highway Capacity Manual (HCM) methods of intersection traffic control analysis with traditional traffic forecasting processes. Although there are many planning agencies that claim to be using HCM procedures, the process described is shown to be the one that much more faithfully replicates the flexible approach capacities and volume/delay relationships that are the direct result of HCM-level analysis.
Utah’s Legal Framework for Corridor Preservation Activities
Authors: Saito Mitsuru , Thomas David A. , Payne Robert S. , Thurgood Glen J.
Published: April 2007

Tools and techniques for corridor preservation strategies are categorized into two groups: interim protection measures and preservation measures. Interim protection measures serve to hold land out of development until it can be purchased; preservation measures definitively ensure that right-of-way will be available when needed for a transportation facility. This almost invariably involves full transfer of title of others’ rights to a public transportation or other government entity. These measures must be implemented within the limits of the statutes that exist in the state where a public agency is located. Whether state officials choose to establish a long-range highway corridor preservation program by acquisition or by police power regulation, that program will be subject to several statutes that generally constrain all such activities. A review of legislation in Utah and other U.S. states that specifically addresses corridor preservation was conducted. It was found that about 20 states had some statutes relating to corridor preservation. In Utah and in other states, however, few state legislative provisions governing long-range preservation activities are orderly or systematic. A summary of findings on legal issues of corridor preservation in Utah and possible ways for enabling long-term corridor preservations so that states that face similar problems can glean insights from Utah’s experience is presented. Also presented is a model legislation that was developed based on study findings in an effort to raise the issue of legal aspects of corridor preservation.