bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanistic-Empirical Approach to Assessing Relative Pavement Damage
Authors: Ioannides Anastasios M. , Karanth Rohit K. , Sanjeevirao Krishnakumar
Published: April 2007

The purpose of this investigation was to examine the feasibility of using conventional pavement analysis tools to derive mechanistic-empirical load equivalency factors (LEFs) applicable to wheel assemblies and pavement cross-sections not included in the AASHTO guide tables in a manner that would provide seamless continuity with current pavement engineering practices. The derivation of such LEFs was pursued on the assumption that two controversial concepts—namely, load equivalency and linear damage accumulation—were, in fact, valid. The purpose of this assumption is to investigate whether it is possible to reach reasonable conclusions for as long as no theoretically valid alternatives to these concepts are available. It was found that it is possible to reproduce with a reasonable fit the statistical/empirical LEFs found in the AASHTO guide tables, using layered elastic analysis and the fatigue relationship derived by Vesic and Saxena. Other conventional fatigue relationships yield unreliable results when compared to the AASHTO LEFs. It is also possible to derive mechanistic-empirical extensions to the AASHTO LEFs using this approach, so tire configurations and pavement cross-sections not included in the AASHTO tables of LEFs can be accommodated in a seamless and equitable manner.
Evaluation of Superlight Pavements Under Accelerated Traffic
Authors: Steyn W. J. vdM. , Sadzik E. S. , De Beer M.
Published: April 2007

In South Africa there is a great need to upgrade the accessibility of rural areas. With the aid of the heavy-vehicle simulator (HVS), the Gauteng Department of Transport and Public Works and the Council for Scientific and Industrial Research (CSIR) investigated the upgrading of in situ gravel roads to the paved standard through addition of a gravel bonding surface layer only. The HVS program consisted of nine tests in which loading and environmental conditions were varied. The results of this investigation indicated that loading and environmental conditions were the dominant influences on the behavior of superlight pavements. An interim transfer function for the design of superlight pavements based on the results of the investigation is provided, together with recommendations for optimization of the transfer function.
Measuring Motorist Comprehension of Florida’s School Bus Stop Law and School Bus Signalization Devices
Authors: Baltes Michael R.
Published: April 2007

Motorists’ knowledge of Florida’s school bus stop law (the Law) and various school bus signalizations was investigated and is summarized. The study focused on determining the level of motorists’ knowledge regarding their driving responsibilities as defined in the Law and the meaning of the various signalizations used on school buses. To gather the necessary information, a simple one-page survey was developed and distributed to a random sample of driver’s license examining offices in the state. Summary statistics indicate that significant confusion exists on the part of motorists regarding their responsibilities as defined in the Law as well as the meaning of the various school bus signalizations. In addition to the reporting of summary statistics, many logistic regression models were developed using the sample data to determine the odds ratios of increasing motorists’ knowledge of the Law and signalizations associated with explanatory variables including age, gender, ethnicity, receipt of a citation for violation of the Law, and recent exposure to safety information about the Law and signalizations via driver training courses, public service announcements (PSAs) on TV or radio, or some other form of electronic or printed media, for example. Findings from some of the models indicate that certain factors significantly increased and decreased the odds of motorists having knowledge of the Law and various signalizations. Recommendations include increasing the awareness of motorists through PSAs, adding questions to driver’s license examinations about stopping for school buses, and decreasing the period of time between required driver’s license renewals.
Comparative Study of Speed Reduction Effects of Photo-Radar and Speed Display Boards
Authors: Bloch Steven A.
Published: April 2007

Two forms of automated motor-vehicle speed control, speed display boards and photo-radar, are compared. Despite a growing body of research on the devices, there is little reliable empirical evidence about their effectiveness. Three issues are examined: ( a) which of these devices is more effective in lowering speeds, ( b) whether supplementing display boards with police enforcement makes them more effective, and ( c) which device is more cost-effective. The study was conducted on three comparable streets in Riverside, California, over a 4-week period. Site 1 employed a display board with no enforcement; Site 2, a display board with intermittent enforcement; and Site 3, photo-radar. Results show that both devices, while deployed, significantly reduce vehicle speeds 7 to 8 km/h, and particularly reduce the number of vehicles traveling 16 km/h (10 mph) or more over the posted limit. Supplementing the display board with intermittent enforcement significantly increased its effectiveness. Although both devices produced substantial speed reductions while in operation, only display boards demonstrated carryover effects. The enforced display board produced a substantial short-term (but not longer-term) carryover effect; the unenforced display board demonstrated a longer-term (but not short-term) carryover effect, but only at the alongside location, 1 week after its removal. The three cost-effectiveness estimates generated showed that the unenforced speed display board was the most cost-effective; the enforced display board came in second; and the photo-radar placed third.
Comparative Evaluation of the Cost-Effectiveness of 58 Transportation Control Measures
Authors: Pansing Cynthia , Schreffler Eric N. , Sillings Mark A.
Published: April 2007

Often when public agencies allocate funding for transportation programs, evaluation of a project’s performance becomes an afterthought, if a consideration at all. Relatively recently, evaluation of project performance has garnered attention as a means for both assessing how cost-effectively public funds help attain transportation and air quality objectives and guiding future public investment decisions. Nonetheless, these efforts suffer at times from a lack of coordination and would benefit from the application of a standardized method. Such a standardized method is applied to evaluate the cost-effectiveness of three categories of transportation control measure (TCM) projects: fixed-route transit, transportation demand management (TDM), and alternative fuel projects. The method provides a means for estimating and quantifying travel mode effects and converting them to net emissions benefits. Three sets of funding programs implemented in California were the subjects of evaluation efforts in which the standardized method was applied. The results of these evaluations are presented, and conclusions are suggested about project cost-effectiveness on the basis of project data and comparisons across categories of projects. On the basis of the evaluation of 58 projects, TDM projects other than telecommunications projects were cost-effective compared with alternative fuel and fixed-route transit projects. In light of the key evaluation findings, an approach and framework for future evaluations of TCM projects to ensure consistency and comparability are proposed. Some future uses of the evaluation data in the form of a centralized database are also suggested.
Experimentally Derived Cost-Effective Planning of Bridge Deck Rehabilitation by Steel Plate Bonding
Authors: Kanno Tadashi , Kamihigashi Yasushi , Ishida Hiromu
Published: April 2007

Rehabilitation cycle is being studied in relation to life-cycle costing based on the realization that making rehabilitation cost-effective would require minimizing the necessary investment. However, the progress of an actual structure’s deterioration cannot be predicted precisely without a collection of inspection data, and therefore, at present the rehabilitation cycle is merely calculated on the idealized progressive deterioration hypothesis. In this study, the optimal life cycle of reinforced concrete deck slabs is derived from the residual life determined through a series of fatigue experiments on deck slabs cut out from existing bridges and rehabilitated afterwards. As a result, precise and cost-effective rehabilitation planning was made possible.
Assessment and Mitigation Measures for Graffiti on Highway Structures
Authors: Eck Ronald W. , Martinelli David R.
Published: April 2007

Highway structures are public works facilities that are inherently accessible, to a certain degree, to the general public at all hours of the day and every day of the year. As a result, some highway structures are susceptible to graffiti. Graffiti on highway structures is a significant problem throughout the United States. Not only is graffiti an eyesore to the traveling public, it presents a hazard to the perpetrator and a liability exposure for transportation agencies because highway structures span high elevations and are in close proximity to motor vehicle traffic. The most common methods for combating graffiti include washing the surface of the structure with high-pressure water sprays, repainting the surface, and sandblasting. Although each of these methods can, in most cases, effectively remove the graffiti, the solution is often temporary; more graffiti is likely to appear in the future at the same site. Further, these measures can be quite costly, especially if they have to be repeated on numerous occasions to remove recurring graffiti. Results of a comprehensive survey of transportation agencies are presented and analyzed. The survey was designed to assess the nature and extent of the graffiti problem as well as to identify some solutions to the problem and identify various preventive as well as removal techniques. The study focuses on current graffiti prevention and removal policies and various other graffiti-removal techniques that are undertaken by different state departments of transportation to mitigate graffiti problems in their states.
Analysis of Pavement Management Activities Programming by Genetic Algorithms
Authors: Fwa T. F. , Chan W. T. , Hoque K. Z.
Published: April 2007

The application of genetic algorithms to programming of pavement maintenance activities at the network level is demonstrated. The operational characteristics of the genetic algorithm technique and its relevance to solving the programming problem in a Pavement Management System (PMS) are discussed. The robust search capability of genetic algorithms enables them to effectively handle the highly constrained problem of pavement management activities programming, which has an extremely large solution space of astronomical scale. Examples are presented to highlight the versatility of genetic algorithms in accommodating different objective function forms. This versatility makes the algorithms an effective tool for planning in PMS. It is also demonstrated that composite objective functions that combine two or more different objectives can be easily considered without having to reformulate the genetic algorithm computer program. Another useful feature of genetic algorithm solutions is the availability of near-optimal solutions besides the "best" solution. This has practical significance as it gives the users the flexibility to examine the suitability of each solution when practical constraints and factors not included in the optimization analysis are considered.
Pavement Preservation Strategy
Authors: Shober Steve F. , Friedrichs David A.
Published: April 2007

An effective pavement management system requires a comprehensive pavement preservation strategy (PPS). Wisconsin’s PPS is guided by a philosophy whose goal is to optimize pavement performance to provide the highest quality service to the customer per unit of expenditure. The PPS is customer-oriented and views “service” in terms of user comfort, convenience, and safety. The strategy is broad-scoped and considers all pavement management activities, from “do nothing” to reconstruction. Wisconsin’s PPS has program values that are based on solid research that has been field verified. The treatment alternatives recommended for any particular pavement problem address the causes, not the symptoms, of that particular problem—thus, the root cause of the problem is addressed, and funds are not used to treat merely a symptom. Accordingly, the PPS is termed a cause-based instead of a schedule-based strategy (applying treatments on a predetermined schedule), or a “worst first” strategy (treating the worst pavements first). The PPS follows a logical progression through a series of evaluations to convert a set of raw, field-collected data (ride and distress) to, ultimately, a set of recommended actions. The process moves from raw data to an evaluation of the level of the distress. Combinations of distress levels are used to identify specific pavement problems. In turn, these pavement problems are evaluated as a family to generate appropriate, cost-beneficial solutions.
“Off-the-Wall” Pavement Distress Variability Study
Authors: Daleiden Jerome F. , Simpson Amy L.
Published: April 2007

Variability of pavement surface distress data collection has always been an area of significant concern. When conducting evaluations of distress data manually (with raters observing pavements in question, interpreting what they see, and recording on paper) the process is subject to human errors. To minimize the impact of such human errors on these important pavement performance data, sophisticated equipment has been developed to eliminate as much of the human intervention as possible. Such technology is not without its own limitations of precision and bias. With both methodologies being used for the collection of surface distress data for the long-term pavement performance (LTPP) program, questions regarding precision and bias have been identified. In attempting to define the variability of the data for incorporation in stochastic analyses, it has become apparent how diverse and complex these distress data truly are. To adequately quantify the precision and bias, a detailed experiment was designed to evaluate the errors inherent in the different distress data collection methodologies. The facet of the experiment reported targets the variability of human distress surveyors and the biases associated with conducting surveys from film, using a slightly different projection system. Specifically, a collection of surveyors was assembled to establish the variability associated with experienced raters versus novice raters, engineers versus engineering technicians, and teams versus individuals.
International Standards Organization-Compatible Index for Pavement Roughness
Authors: Papagiannakis A. T. , Raveendran B.
Published: April 2007

The development of a new pavement roughness index, which is compatible to the current International Standards Organization (ISO) standard on “exposure to whole-body vibration” is described. The index was intended to be the independent variable in the future development of relationships between user cost (i.e., vehicle depreciation, repairs, discomfort and so on) and pavement roughness; hence it was named RIDE (Roughness Index for Driving Expenditure). RIDE is based on the sprung mass acceleration response of a reference vehicle to the pavement profile. It is calculated in the frequency domain by multiplying the power spectral density (PSD) of the pavement profile by the square of the transfer function of the sprung mass acceleration of the reference vehicle. The resulting sprung mass acceleration PSD is integrated over frequency to yield the root-mean-square of the sprung mass acceleration per unit length of pavement traveled. The sprung mass acceleration is shown to be the main contributor of dynamic axle loads in heavy trucks, which relate to vehicle and cargo damage and also to pavement damage.
Introducing Buses into First-Order Macroscopic Traffic Flow Models
Authors: Lebacque J.P. , Lesort J.B. , Giorgi F.
Published: April 2007

The aim of this paper is to provide a simple model of the interaction between buses and the surrounding traffic flow. Traffic flow is assumed to be described by a first-order macroscopic model of the Lighthill-Whitman-Richards type. As a consequence of their kinematics, which in large measure can be considered to be independent of the flow of other vehicles, buses should be considered as a moving capacity restriction from the point of view of other drivers. This simple interaction model is analyzed, mainly by considering the moving frame associated with the bus in order to derive analytical computation rules for derivation of the effects of the presence of the bus in the traffic flow. After deriving traffic equations in the moving frame associated with a bus, the usual basic concepts of first-order models, including those of relative traffic supply and demand, are generalized to the moving frame. A simple model for the bus-traffic interaction, assuming that the dimension of the bus can be neglected, can be derived from analytical calculations in the moving frame. Finally, some tentative results for the inclusion of buses into first-order traffic flow models, discretized according to Godunov’s scheme, are given.
Continuous Learning Framework for Freeway Incident Detection
Authors: Peeta Srinivas , Das Debjit
Published: April 2007

Existing freeway incident detection algorithms predominantly require extensive off-line training and calibration precluding transferability to new sites. Also, they are insensitive to demand and supply changes in the current site without recalibration. We propose two neural network-based approaches that incorporate an on-line learning capability, thereby ensuring transferability, and adaptability to changes at the current site. The least-squares technique and the error back propagation algorithm are used to develop on-line neural network-trained versions of the popular California algorithm and the more recent McMaster algorithm. Simulated data from the integrated traffic simulation model is used to analyze performance of the neural network-based versions of the California and McMaster algorithms over a broad spectrum of operational scenarios. The results illustrate the superior performance of the neural net implementations in terms of detection rate, false alarm rate, and time to detection. Of implications to current practice, they suggest that just introducing a continuous learning capability to commonly used detection algorithms in practice such as the California algorithm enhances their performance with time in service, allows transferability, and ensures adaptability to changes at the current site. An added advantage of this strategy is that existing traffic measures used (such as volume, occupancy, and so forth.) in those algorithms are sufficient, circumventing the need for new traffic measures, new threshold parameters, and variables that require subjective decisions.
Method of Successive Averages Versus Evans Algorithm: Iterating a Regional Travel Simulation Model to the User Equilibrium Solution
Authors: Walker W. Thomas , Rossi Thomas F. , Islam Nazrul
Published: April 2007

The results of comparative tests of two methods for iterating a regional travel demand model system are presented. Model iteration is necessary to ensure consistency between model input and output speeds, as required by current federal legislation. Two methods were tested: the Evans algorithm and the method of successive averages. A series of tests using alternative assignment techniques was conducted for each method. Criteria for evaluating the iteration methods included convergence error, average highway speeds compared with observations, highway vehicle miles traveled compared with Highway Performance Monitoring System estimates, transit boardings compared with observations, and computer running time. It was concluded that the Evans algorithm performed the best, primarily on the basis of superior computational efficiency, although good results were obtained by using the method of successive averages. Use of the Evans algorithm is recommended, embedded within a formal assignment restart, for iterating the model system. Multiple iterations of highway assignment should be used in the initial model loop and all-or-nothing assignments in subsequent iterations of the modeling chain.
Multinomial Probit with Structured Covariance for Choice Situations with Similar Alternatives
Authors: Yai Tetsuo , Shimizu Tetsuo
Published: April 2007

The estimatability of the multinomial probit (MNP) model has been improved greatly by the modeling of the error structure. A modeling idea for travelers’ choice behaviors using the MNP with structured covariances (MNPSC) model is proposed. Choice of route, destination, and time of day are considered. The covariance of the error term of the utility function is structured by introducing the overlapped length between any two routes and the overlapped time length between any two departure times. Simultaneous models such as route and train class, route and mode, and time of day and mode choice model also are introduced by applying the MNPSC modeling idea. These are formulated easily by assuming that the error is generated independently between two choices. An empirical study for a route and train class choice model was conducted by using the passenger survey data in the Tokyo metropolitan region, and its estimatability and applicability are examined.
Investigation of Stochastic Network Loading Procedures
Authors: Prashker J. N. , Bekhor S.
Published: April 2007

The network loading process of stochastic traffic assignment is investigated. A central issue in the assignment problem is the behavioral assumption governing route choice, which concerns the definition of available routes and the choice model. These two problems are addressed and reviewed. Although the multinomial logit model can be implemented efficiently in stochastic network loading algorithms, the model suffers from theoretical drawbacks, some of them arising from the independence of irrelevant alternatives property. As a result, the stochastic loading on routes that share common links is overloaded at the overlapping parts of the routes. Other logit-family models recently have been proposed to overcome some of the theoretical problems while maintaining the convenient analytical structure. Three such models are investigated: the C-logit model, which was specifically defined for route choice; and two general discrete-choice models, the cross-nested logit model and the paired combinatorial logit model. The two latter models are adapted to route choice, and simple network examples are presented to illustrate the performance of the models with respect to the overlapping problem. The results indicate that all three models perform better than does the multinomial logit model. The cross-nested logit model has an advantage over the two other generalized models because it enables performing stochastic loading without route enumeration. The integration of this model with the stochastic equilibrium problem is discussed, and a specific algorithm using the cross-nest logit model is presented for the stochastic loading phase.
Dynamic Aspects of Commuter Decisions Under Advanced Traveler Information Systems: Modeling Framework and Experimental Results
Authors: Liu Yu-Hsin , Mahmassani Hani S.
Published: April 2007

Previous work on the effect of advanced traveler information systems was concerned primarily with immediate route choice decisions in response to real-time traffic information. Real-time traffic information also influences day-to-day decisions of trip makers, including departure time and route choices. Joint departure time decision and pretrip route selection are addressed, as well as en route path switching behavior by commuters under real-time information availability. Data were used from laboratory experiments using a dynamic interactive traveler simulator that allows actual commuters to simultaneously interact with each other within a simulated traffic corridor. Given real-time information provided by the system, commuters determine their departure time and route at the origin and select paths en route at various decision nodes along the trip. Day-to-day dynamic models of commuters’ joint departure time and route switching decisions are developed and calibrated by using a multinomial probit model framework that takes into account commuters’ learning from experience. The analysis provides insight into day-to-day effects of real-time traffic information on user decisions. Results indicate that the reliability of real-time information and supplied schedule delay (relative to the commuters’ preferred arrival time) are significant variables that influence users’ indifference band governing route switching behavior both pretrip and en route. These models are intended for use within evaluation frameworks (e.g., simulation-assignment models). In addition, the substantive insights provide guidelines for the design of real-time information content and systems.
Discrete Dynamic Shortest Path Problems in Transportation Applications: Complexity and Algorithms with Optimal Run Time
Authors: Chabini Ismail
Published: April 2007

A solution is provided for what appears to be a 30-year-old problem dealing with the discovery of the most efficient algorithms possible to compute all-to-one shortest paths in discrete dynamic networks. This problem lies at the heart of efficient solution approaches to dynamic network models that arise in dynamic transportation systems, such as intelligent transportation systems (ITS) applications. The all-to-one dynamic shortest paths problem and the one-to-all fastest paths problems are studied. Early results are revisited and new properties are established. The complexity of these problems is established, and solution algorithms optimal for run time are developed. A new and simple solution algorithm is proposed for all-to-one, all departure time intervals, shortest paths problems. It is proved, theoretically, that the new solution algorithm has an optimal run time complexity that equals the complexity of the problem. Computer implementations and experimental evaluations of various solution algorithms support the theoretical findings and demonstrate the efficiency of the proposed solution algorithm. The findings should be of major benefit to research and development activities in the field of dynamic management, in particular real-time management, and to control of large-scale ITSs.
Accuracy and Performance of Improved Speed-Flow Curves
Authors: Dowling Richard G. , Singh Rupinder , Wei-Kuo Cheng Willis
Published: April 2007

Skabardonis and Dowling recommended updated Bureau of Public Road speed-flow curves for freeways and signalized arterials to improve the accuracy of speed estimates used in transportation demand models. These updated curves generally involved the use of higher power functions that show relatively little sensitivity to volume changes until demand exceeds capacity, when the predicted speed drops abruptly to a very low value. Skabardonis and Dowling demonstrated that the curves provide improved estimates of vehicle speeds under both uncongested and queueing conditions; however, they did not investigate the impact of these curves on the performance of travel demand models. Practitioners have been concerned about the impacts of such abrupt speed-flow curves on the performance of their travel demand models. Spiess has stated that higher power functions are more difficult computationally for computers to evaluate and that more abrupt speed-flow curves adversely affect the rate of convergence to equilibrium solutions in the traffic assignment process. In this paper the impact of the Skabardonis and Dowling updated speed-flow curves on the performance of selected travel demand models is investigated. The updated speed-flow curves were found to significantly increase travel demand model run times. However, it is demonstrated that an alternative speed-flow equation developed by Akçelik has similar or better accuracy and provides much superior convergence properties during the traffic assignment process. The Akçelik curve significantly reduced travel demand model run times.
Safety, Delay, and Capacity of Single-Lane Roundabouts in the United States
Authors: Flannery Aimee , Elefteriadou Lily , Koza Paul , McFadden John
Published: April 2007

Roundabouts are a form of at-grade intersection control that is used frequently around the world and is becoming popular in the United States. Roundabouts are being used to replace two-way and all-way stopcontrolled intersections and traffic signals in the United States. Roundabouts have also been used recently in Vail, Colorado, to improve an existing stop-controlled freeway interchange system. In this study, five single-lane roundabouts are studied to assess their safety and operational performance. All five sites were stop-controlled before roundabouts were installed, and overall the sites experienced a reduction in accident frequencies, rates, and also control delay. Aside from a review of safety and delay data before and after installation of the roundabouts, this study includes a comparison of field-measured control delay with that predicted by SIDRA, an analytically based software package that can analyze at-grade sign- and signal-controlled intersections as well as roundabouts. This study will help agencies better understand their ability to predict delay at American roundabouts. Finally, findings are presented regarding the accuracy of the roundabout capacity model contained in the 1997 update to Chapter 10 of the Highway Capacity Manual. Because of the lack of roundabout entries that are operating at capacity in the United States, an approximation of potential capacity based on available gaps in the circulating stream was made. These findings indicate that the manual may be optimistic in its prediction of capacity for single-lane roundabouts in the United States; however, it should be noted that the lack of roundabout entries operating under capacity in the United States only allows for an approximation of field capacity to be made at this time.
Queueing at Congested Intersections
Authors: Troutbeck Rod , Blogg Miranda
Published: April 2007

The operation of intersections when conditions are changing rapidly or if demand exceeds capacity has been a point of discussion for a long time. Most techniques for predicting delays and queue lengths have been based on the so-called coordinate transform approach. Discussed in this paper are the relationships from the coordinate transform method and their shortcomings. Also, the issues are explained and theoretical solutions described that are based on the diffusion theory by Newell, which provides an improved estimate of average queue length and, more importantly, gives the variance of the queue length. It is concluded that Newell’s approach provides better estimates of the mean and variance of the queue length. Using the mean as well as the variance provides better methods to predict the performance of the system.
Analysis of Gauging Station Flood Frequency Estimates in Nebraska Using L-Moments and Region of Influence Methods
Authors: Provaznik Mary Kay , Hotchkiss Rollin H.
Published: April 2007

Recent advances in predicting flood magnitude and frequency at streamgauging stations are illustrated using stream flow data from Nebraska. Prediction methods were based on statistical techniques referred to as L-moments and the region of influence method (ROI). L-moments are less sensitive to extremely high or low floods than current procedures and may provide more stable estimates of flood frequency. The ROI method for predicting flood frequency does not depend on fixed hydrologic regions but uses information from all appropriate gauges in the state to form a unique region and frequency estimate for each site. Estimates of the 100-year flood using current procedures showed statistically significant differences from estimates made using a generalized extreme value distribution with L-moments. Differences were due to the treatment of extreme flood events and illustrate the robust character of L-moments. L-moments were less sensitive to extreme floods as expected. Creating regions using the ROI method was found to be sensitive to the selection of basin attributes for assembling sites, but was not sensitive to the number of gauges initially used to create a region, nor the criterion used to eliminate a gauge from a potential region. Statistical tests revealed insignificant differences between ROI estimates of the 100-year flood when compared with estimates using current procedures. The similarity in estimates is attributed to current “filtering” procedures used that reduce the impact of extreme events. The ROI method is viewed as a more objective method of achieving the same result.
Development of a 100-km/h Reusable High-Molecular Weight/High-Density Polyethylene Truck-Mounted Attenuator
Authors: Carney John F. , Chatterjee Subhasish , Albin Richard B.
Published: April 2007

A reusable truck-mounted attenuator has been developed that dissipates kinetic energy through the lateral deformation of a nested cluster of high-molecular weight/high-density polyethylene cylinders. This 100-km/h impact attenuation device, called the Vanderbilt truck-mounted attenuator (VTMA), satisfies the crash testing requirements of NCHRP Report 350. It has been approved by the Federal Highway Administration for use on the national highway system under these NCHRP Report 350 guidelines. Most impact attenuation devices currently employed require the replacement of damaged structural components and spent-energy-dissipating elements following an impact event. Until these repairs and refurbishments are carried out, these safety devices are largely ineffective because they are unable to dissipate kinetic energy in a subsequent impact in an acceptable manner such that relevant occupant risk parameters are within prescribed limits. The VTMA is a reusable and self-restorative truck-mounted attenuator. It can dissipate large amounts of kinetic energy, undergo significant deformations and strains without fracturing, and then, essentially, regain its original shape and energy-dissipation potential on removal of the load. The VTMA design was optimized through finite-element modeling using DYNA3D. This inexpensive modeling tool resulted in a reduction in the number of expensive full-scale crash tests required to develop the system. Computer modeling can optimize the probability for success of a given full-scale crash test, removing the trial-and-error approach to appurtenance design.
Side-Impact Crash Test and Evaluation Criteria for Roadside Safety Hardware
Authors: Ray Malcolm H. , Hargrave Martin W. , Carney John F. , Hiranmayee K.
Published: April 2007

During the past decade, reducing the severity of side-impact collisions has been an emerging area of research by a variety of organizations and research communities. The motor vehicle manufacturing and regulatory communities in the United States, Europe, and many other countries have developed dynamic side-impact test and evaluation criteria to reduce the severity of vehicle-to-vehicle side-impact collisions. Similarly, the international research community has developed test procedures for performing impacts into poles, one of the most severe types of side-impact collisions. Preliminary side-impact test and evaluation procedures have been conducted for roadside safety hardware, like guardrails, guardrail terminals, luminaire supports, utility poles, and signs. Recommendations for performing roadside hardware side-impact crash tests are summarized; the results of several side-impact roadside hardware crash tests are described; the proposed test and evaluation procedures are compared with other major side-impact test and evaluation procedures; and areas requiring further research are discussed.
Validation of a Four-Quadrant Gate Simulation Model: Predicted Versus Actual Gate Operating Values
Authors: Coleman Fred , Moon Young J.
Published: April 2007

Coleman and Moon demonstrated a traffic engineering-based design methodology to determine gate delay (length of flashing signal operation prior to entry gate descent) and gate interval time (time period between initiation of descent of entry gates and initiation of descent of exit gates) at four-quadrant gate crossings. A simulation model incorporating this traffic engineering-based design methodology was developed for the Illinois Department of Transportation to assist in establishing four-quadrant gate operating parameters. To assist in validating the four-quadrant gate simulation model, a comparison of the gate operating parameters at a recent installation in North Carolina was undertaken. The findings from the comparison indicate there is close agreement with the values used in the field installation and those determined by the simulation model.
Method of Obtaining Consumer Welfare from Regional Travel Demand Models
Authors: Rodier Caroline J. , Johnston Robert A.
Published: April 2007

The need for more comprehensive traveler welfare measures is highlighted by the U.S. Intermodal Surface Transportation Efficiency Act (1991) requirement that transportation projects and plans be evaluated for economic efficiency. However, to date, there has been a discrepancy between this requirement and the methods used by regional transportation organizations to evaluate transportation policies in the United States. Kenneth Small and Harvey Rosen illustrate how a consumer welfare measure known as compensating variation can be obtained from discrete choice models. A method of application is developed for the mode choice models in the Sacramento Regional Travel Demand Model. The results of the method’s application to the model for light rail transit, high-occupancy vehicle lanes, and auto pricing scenarios are examined for both total consumer welfare and consumer welfare by income class.
Commercial Development at Rural and Small-Town Interstate Exits
Authors: Hartgen David T. , Kim Ji Youn
Published: April 2007

Commercial development at 63 rural and small-town Interstate exits is quantified and related to local market wealth, size, geography, access, traffic, site competition, and other development. Five development types (gas stations, convenience stores, fast food restaurants, sit-down restaurants, and motels) are studied. The geographic information system TransCAD 3.0 is used to determine network access and local trade area characteristics. Models are then estimated for each development type using classification and regression techniques separately and in combination. Model estimates are then compared with actual development. Results show that the relationships are complex, often nonlinear; and show high correlation between development types. The findings should be useful for planning exit land use, coordinating market assessments, determining the value of land, and assessing sites for business placement.
Applying Benefit/Cost Analysis To Identify and Measure the Benefits of Intelligent Transportation Systems
Authors: Brand Daniel
Published: April 2007

The guidance provided by benefit/cost analysis (BCA) is used to identify the measures appropriate for assessing the benefits of intelligent transportation systems (ITS) investments using BCA. Proper recognition of how ITS differs from conventional transportation improvements can avoid expensive data collection, serious underestimates of the benefits of ITS, and mistakes in our planning and investment policies. The steps in BCA are described, including its strict rules governing the inclusion of benefit measures. An ITS causal model chain is presented that links the five traditional ITS goals (efficiency, mobility, safety, productivity, and energy/environment). The model chain varies from the conventional planning model because the ITS mobility and productivity benefit measures do not vary directly with its safety, energy, and environmental impacts. Recommendations are given for avoiding double counting ITS mobility and productivity benefits, and for identifying them correctly. Errors in valuing the mobility benefit using observed data on travel and ITS product and service buying behavior are described, as is the potential for serious underestimates of ITS mobility benefits from using observed or predicted travel time savings as the primary mobility benefit measure. Instead, direct measurement and valuation of the ITS mobility benefit using customer satisfaction (stated preference) survey methods avoid the problems of ( a) how exactly to measure the utility-generating features of ITS user benefits, and ( b) observing the behavioral responses to ITS information, which involve expensive data collection. Measuring customer satisfaction directly can also simplify other areas of ITS evaluation, including avoiding traditional transportation modeling in some instances.
Best Neighbor Heuristic Search for Finding Minimum Paths in Transportation Networks
Authors: Adler Jeffrey L.
Published: April 2007

For a wide range of transportation network path search problems, the A* heuristic significantly reduces both search effort and running time when compared to basic label-setting algorithms. The motivation for this research was to determine if additional savings could be attained by further experimenting with refinements to the A* approach. We propose a best neighbor heuristic improvement to the A* algorithm that yields additional benefits by significantly reducing the search effort on sparse networks. The level of reduction in running time improves as the average outdegree of the network decreases and the number of paths sought increases.
Axiomatic Approach To Developing Partial Automation Concepts for Deployment of Automated Highway Systems and Partial Invocation of Vision-Based Lane-Keeping and Adaptive Cruise Control
Authors: Jacob Tsao H.-S.
Published: April 2007

Discussions about the pros and cons of the automated highway system (AHS) visions are nothing but intellectual exercises unless the issue of how to evolve the current highway system toward this end state can be resolved. The primary motivation for the AHS is its potential for considerable highway capacity gain without major acquisition of right-of-way. Many believe that such capacity gain is possible only when lanes are dedicated to the use of those vehicles equipped for full automation. However, to avoid the empty-lane syndrome, there must exist a sufficient population of automation-equipped vehicles that can use the dedicated lane at once or shortly thereafter. Also, if such automation-equipped vehicles can be used only on such dedicated lanes, few people would purchase such vehicles before dedication of lanes on a network basis, the well-known “chicken-and-egg” problem. In this paper partial-automation concepts are proposed that help solve this chicken-and-egg problem. Because of the futuristic nature of the AHS, many technological and nontechnological questions cannot be answered definitely. Assumptions must first be made about the likely or reasonable answers to such questions and then requirements derived for partial-automation concepts based on these assumptions. The goal is for the inferencing process to be rigorous and correct so that only the assumptions are to be debated. The author believes that the assumptions made are reasonable and therefore that the requirements for partial-automation concepts and the actual partial-automation concepts proposed are necessary. Most important, it is hoped that this approach will facilitate a more rigorous process in exchanging ideas and debating AHS deployment issues.
Training and Technology Transfer for Low-Volume Roads in Developing Countries
Authors: Miles Derek W. J.
Published: April 2007

Experience in promoting suitable technologies and improving operational performance is drawn on to enable developing countries to make more effective use of local resources in the construction and maintenance of low-volume roads. Training and technology transfer projects require multidisciplinary consulting and advisory support, which may include courses and on-the-job training but may also require “twinning” and other linkages between institutions for a more substantial transfer of skills over a longer period. The process is illustrated by case studies from a range of national and international technical cooperation projects, including the global Management of Appropriate Road Technology research initiative and the World Road Association’s World Interchange Network. The cases are set within a framework of basic models of ways in which training and technology transfer can contribute to international construction industry development, which suggests an inverse relationship between project predictability and recipient autonomy. The analysis offers several general lessons for engineers involved in international technology transfer, including ( a) the importance of assessing local administrative, social, cultural, and regulatory environments at the project design stage; ( b) the need for an open-minded approach to the choice of technology; ( c) the scope for working with and through the local private sector; ( d) deciding on an appropriate mix of technical and management training; and ( e) applying the principle of sustainability through recognition of recipient autonomy and maintained contact between provider and recipient institutions to build confidence through collaboration.
Developments in Innovative Low-Volume Road Technology in Botswana
Authors: Pinard M. I. , Obika B. , Motswagole K. J.
Published: April 2007

Botswana is characterized by a number of features, including its vast size, small and spatially dispersed population, scarcity of conventional road building materials, near absence of surface water, and climatic extremes, which combine to pose a major challenge to economic road construction. This has dictated a need for developing innovative approaches to road technology in circumstances in which conventional approaches often are prohibitively costly and inappropriate for direct application to local conditions. Presented are several innovative, cost-saving approaches to road technology in Botswana that have been developed through several decades of research with the aim of optimizing the use of locally available resources. The applicability of these techniques in similar environments with a semiarid climate also is discussed and the need for caution when using standard specifications in areas such as Botswana is highlighted.
Development of a Field Evaluation Guide for Unpaved Rural Roads
Authors: Calvert Eugene C. , Haiar Keith , Wilson Eugene M.
Published: April 2007

The need of local road managers to have a readily accessible reference guide for identifying deficiencies and improving safety on low-volume roads has prompted the development of a field guide for unpaved rural roads. Technical resources are available to evaluate the various aspects of a low-volume road. However, the resources are in numerous publications and not in a single, easy-to-use document. The concept of the field guide is to provide a single reference to assist rural road managers in making on-site evaluations of specific roadway deficiencies. Critical safety issues and unpaved rural road responsibilities vary throughout the United States. A national focus group was used to recognize this variability. A modified Delphi survey procedure was used to facilitate focus group input and review the project. The Wyoming Technology Transfer Center, in cooperation with the FHWA Local Technical Assistance Program, was responsible for development of the guide. Reviewed are the steps and considerations taken in the development of the guide. Developmental techniques, such as input from a national focus group of transportation professionals, were used to successfully complete this project. The methodologies used to develop this guide are applicable and potentially useful for completing other transportation projects worldwide.