bluuebunny/crossref_metadata_2025 huggingface dataset:
Designing an Effective Approach to the Public: Alaska’s Experience
Authors: Dilley Marti , Gallagher Tom
Published: April 2007

Public involvement is no longer an option in transportation planning; the public and the Intermodal Surface Transportation Efficiency Act (and the Transportation Equity Act for the 21st Century) require it. In 1996, the Alaska Department of Transportation and Public Facilities (ADOT) responded by engaging the public in designing a new public-involvement procedure (PIP). ADOT first created a process to gather the public’s ideas about how they wanted to be involved—based in part on methods recommended by FHWA and FTA—and then used the process to develop the PIP. A special effort was made to select methods that would help ADOT engage Alaska’s indigenous people, many of whom live in remote villages. The methods in the revised PIP strongly reflected public suggestions: display-poster announcements in rural communities, toll-free telephone and fax numbers, a website with current information, an interactive newsletter, televised and radio call-in programs targeted to rural areas (to complement public meetings in regional centers), and two public committees. The first committee was a small 24-member Policy Advisory Committee; the second was a large 600-member Public Review Group. In 1997–1998, ADOT tested the new procedure in revising the long-range statewide transportation plan. The process that ADOT used to develop the PIP can be used by other agencies; the content of the final PIP, however, will vary with public input. The new PIP has improved ADOT’s public image and appears to have garnered new public support for transportation in general.
Importance of Public Involvement: A Look at Car-Free City Policy in The Netherlands
Authors: Nederveen A. A. J. , Sarkar Sheila , Molenkamp Lindy , Van de Heijden R. E. C. M.
Published: April 2007

A car-free policy for city centers is being widely implemented in the Netherlands. Many of the downtowns have restricted vehicular access to improve the quality of life and to protect the historic city centers. This policy has been extremely popular among center-city residents, who have greatly benefited from a better quality of life and an increase in real-estate prices. The residents in the neighboring areas, however, are unhappy with the negative spillover impacts of this policy and think that, in some ways, the policy is discriminatory. One of the major problems encountered by the residents living close to the car-free centers is the acute parking shortage. The vehicle restrictions and paid-parking enforcement in the car-free downtowns have encouraged many downtown visitors, shoppers, and workers to park in the neighboring areas close to the downtown area. Increased demand for the limited on-street parking has caused major inconvenience to these residents, who believe that the car-free policy is inequitable. Furthermore, they believe that the solution (paid-permit parking) being introduced by the local governments to address the parking crisis is unsatisfactory. Representatives of some of the residential neighborhoods were interviewed, and parking-related problems and issues that these residential neighborhoods face are summarized. Solutions are offered to mitigate the problems faced by the cities.
Research and Development Program for Integrated Urban Models
Authors: Miller Eric J. , Kriger David S. , Hunt John Douglas
Published: April 2007

The case is presented for a new, coordinated research and development (R&D) program designed to improve significantly the operational state of practice in integrated urban modeling. First, the authors’ view of an “ideal” integrated urban modeling system is described. If developed, this modeling system should be capable of incorporating the best possible understanding of transportation and land use interactions and of addressing planning and analysis needs. Also discussed briefly are current operational modeling capabilities as related to the proposed ideal model. Finally, a multiyear R&D program that was designed to move current practice significantly toward the operationalization of the ideal model is detailed.
Light-Rail-Transit Impacts in Portland: The First Ten Years
Authors: Dueker Kenneth J. , Bianco Martha J.
Published: April 2007

The ways in which the first decade of light-rail transit (LRT) in the Portland region have affected auto ownership, mode share, density, and property values are examined. Empirical analysis provides evidence that light rail has had some positive effects on single-family property values, transit use, and slower growth of two-plus car households in the outer part of the LRT corridor as compared with an outer part of a parallel bus corridor. These effects might be the result of households self-selecting to locate near LRT rather than the result of current households changing their mode. This assessment of the evidence indicates the extent to which consumer preferences have responded to LRT investments. This kind of assessment is needed to provide the basis for estimating travel-mode shares and market shares for dispersed and concentrated development forms. Examination of data suggests that it might be advisable for planners to entertain more modest expectations of LRT.
Firm Location in the MEPLAN Model of Sacramento
Authors: Abraham J. E. , Hunt J. D.
Published: April 2007

MEPLAN land use and transportation-interaction models traditionally include models of business-location choice. The mechanisms in the model that allow for realistic aggregate assignment of firms to zones, and the resulting impact that firm location has on the entire modeling system, are described. The models use a form of logit function to allocate production activities to zones. Interdependencies in the Social Accounting Matrix, together with trip- and land-cost data and usage rates, generate a utility function for the attractiveness of purchasing a given sector’s output from a given zone. The alternative specific constants and the dispersion parameter are estimated in calibration, based primarily on cost data, trip-length distributions, and arrangement of activity in a calibration year. Results from a model of Sacramento show the various features and strengths of the model, while pointing out some weaknesses and potential pitfalls. The strengths include the realistic representation of current and continuing patterns, the close linkages between different industry and household types, and the market-based nature of the model. The weaknesses include the aggregate nature of the model and the possibility of difficulties in establishing realistic, alternative, specific constants.
Policy Analysis Using the Sacramento MEPLAN Land Use–Transportation Interaction Model
Authors: Abraham J. E. , Hunt J. D.
Published: April 2007

A land use and transportation interaction model was developed for the Sacramento, California, region, using the MEPLAN framework. The model represents land markets directly together with location-choice processes of different industry and household categories and the interactions among them. These resulting economic interactions lead to trip matrixes that are assigned to a multimodal, capacity-restrained transportation network, generating travel times and disutilities that influence the location-choice process in the period from 1990 to 2015. A range of different policy options is simulated for that period. Five different scenarios are compared with a trend scenario, three representing different long- and short-term government transportation supply scenarios, one representing incentives and disincentives to encourage land use patterns complementary to an improved transit system, and one combining the land-incentive scenario with higher prices for private vehicle use. The scenario predictions differ in mode choice, firm location, residential location, development patterns, vehicle kilometers traveled, and land rents. Various land uses are seen to be bidding against each other, and the differences in spatial arrangements between scenarios are quite complex and demonstrate the richness of the model. Certain changes take time to develop, demonstrating the need for a long-term approach to planning.
SafeStat: Motor Carrier Safety Status Measurement System
Authors: Madsen David G. , Wright Donald G.
Published: April 2007

In 1993, the U.S. Department of Transportation’s Volpe National Transportation Systems Center (the Volpe Center) began a multiyear research effort to propose an improved process for assessing motor carrier safety fitness for the Federal Highway Administration’s Office of Motor Carriers (OMC). At the time, OMC’s primary method of determining safety fitness came from ratings based on the results of onsite safety compliance reviews. The intent of OMC was to take advantage of improved safety data reporting, information systems technologies, and the Volpe Center’s experience in safety measurement methodology, as well as to address the weaknesses of the rating process. The Volpe Center proposed using an automated safety performance monitoring system and subsequently developed SafeStat (Motor Carrier Safety Status Measurement System) as part of a federal-state pilot program. Since then, SafeStat has been implemented nationally by OMC to rank individual motor carriers for compliance reviews. SafeStat is designed to incorporate current on-road safety performance information and enforcement history with the compliance review information to measure the overall relative safety fitness of interstate carriers. In arriving at this overall assessment, SafeStat evaluates carriers in four safety evaluation areas: accident, driver, vehicle, and safety management. SafeStat enables OMC to quantify and monitor the safety status of carriers continually, thereby allowing OMC enforcement and education programs to efficiently allocate resources to carriers that pose a high risk of crashes. The methodology and the current and proposed uses of SafeStat are described.
Resilient Modulus Measurement of Fine-Grained Subgrade Soils
Authors: Muhanna A. S. , Rahman M. S. , Lambe P. C.
Published: April 2007

The effects of several variables that may influence the resilient modulus of fine-grained subgrade soils have been studied using two different soils. The number of load applications, the rest period, and the load sequence are shown to have no significant effect on the measured resilient modulus. It is also demonstrated that confining pressure in the range of 0 to 69 kPa (0 to 10 psi) has less than a 5 percent effect on the measured resilient modulus of the investigated soils. However, the condition of specimen ends is shown to influence the measured resilient modulus. A comparison between the measured resilient modulus for both soils using impact and kneading compaction methods is also presented.
Laboratory Determination of Anisotropic Aggregate Resilient Moduli Using an Innovative Test Device
Authors: Tutumluer Erol , Seyhan Umit
Published: April 2007

The importance of anisotropic aggregate behavior is presently not considered in material characterization for pavement design because of the lack of proper laboratory equipment and testing capabilities. A newly acquired, innovative triaxial testing machine, referred to as the University of Illinois FastCell (UI-FC), was used to determine in the laboratory the anisotropic resilient properties of granular materials. Since the UI-FC permits stresses to be cycled independently in the vertical and horizontal directions, it is ideally suited for simulating dynamic stresses on a sample and for studying the effects of anisotropic stress-path-dependent aggregate behavior. Preliminary results obtained from four aggregates tested using UI-FC indicated definite directional dependency (anisotropy) of aggregate moduli. The resilient moduli computed in the vertical and radial directions varied pronouncedly with the applied stress states. However, when the same procedure was used to test a synthetic specimen having isotropic material properties, the axial and radial stiffnesses computed from the measured resilient deformations remained unchanged. The vertical moduli were typically higher than the horizontal moduli for most aggregates tested, except for a sandy gravel having a significant amount of fines. The testing procedures that were followed, that is, the order of vertical and horizontal pulsing on the specimens, also seemed to influence the computed anisotropic moduli. More anisotropic testing of this nature should be undertaken to investigate the directional dependency of aggregate stiffnesses.
Structural Numbers for Reclaimed Asphalt Pavement Base and Subbase Course Mixes
Authors: MacGregor Jennifer A. C. , Highter William H. , DeGroot Don J.
Published: April 2007

The 1993 AASHTO pavement design guide equation for flexible pavement structures requires the determination of a structural number, which is a function of the layer coefficient, thickness, and drainage coefficient of each layer of pavement. Empirical correlations for layer coefficients have been developed based on resilient moduli. The principal factor affecting the drainage coefficient is the hydraulic conductivity. The objective was to determine how the layer and drainage coefficients of Massachusetts Highway Department (MHD) base and subbase aggregates would be affected by the introduction of reclaimed asphalt pavement (RAP). MHD gray, dense, graded, crushed-stone base and gravel-borrow subbase were combined with 0 to 50 percent RAP (by weight); 9 mixtures were tested, and 27 resilient modulus and 12 hydraulic conductivity tests were conducted. Results from the resilient modulus tests indicate that the resilient moduli of the RAP/base and RAP/subbase mixtures generally increased with an increase in the percentage of RAP. Therefore, the layer coefficient and the structural number increased. The hydraulic conductivity of the RAP/crushed-stone base was not affected by the percentage of RAP in the mixture, but the hydraulic conductivity of the RAP/gravel-borrow subbase increased with an increase in the percentage of RAP. Nonlinear elastic analyses of typical MHD pavement structures indicated a small increase in the structural number with an increase in the percentage of RAP in the base and subbase. Therefore, the addition of RAP to the base and subbase materials tested is considered to be beneficial.
Durability Effects on Resilient Moduli of Stabilized Aggregate Base
Authors: Zaman Musharraf M. , Zhu Jian-Hua , Laguros Joakim G.
Published: April 2007

The effect of wetting/drying and freezing/thawing on the resilient modulus values of Meridian limestone aggregate stabilized with cement-kiln-dust is investigated. Freezing/thawing is found more detrimental than wetting/drying at low deviator stresses. In addition, the stabilized aggregate suffers greater strength reduction during the initial stages of the freeze/thaw test. On the other hand, wetting/drying produces greater strength reduction at high deviator stresses. The layer coefficients of the stabilized aggregate base, which are significantly higher than those of the raw aggregates, are reduced appreciably due to freezing/thawing and wetting/drying.
Evaluation of Laboratory and Backcalculated Resilient Moduli from the Wes Track Experiment
Authors: Mikhail Magdy Y. , Seeds Stephen B. , Alavi Sirous H. , Ott Weston C.
Published: April 2007

Resilient modulus is a critical material property required for the characterization of pavement layers used in modern mechanistic-based pavement design. Because of its fundamental nature, resilient modulus provides a meaningful basis for simulating the effect that an individual layer has on pavement response and performance. Resilient modulus can be determined by laboratory testing or by an analytical procedure known as backcalculation involving the interpretation of nondestructive testing. Unfortunately, resilient modulus results determined from laboratory testing and those determined from backcalculation generally do not agree. The issue of characterizing in situ moduli is addressed by presenting the results of an analysis and comparison of resilient modulus values determined from laboratory testing and those established through backcalculation of falling weight deflectometer (FWD) data from the WesTrack experiment in northern Nevada. These two basic methodologies for resilient modulus determination are reviewed, and many of their known weaknesses and limitations are identified. The backcalculated modulus values were determined using Washington State Department of Transportation’s EVERCALC computer program and FWD data obtained from WesTrack pavement sections at the onset of truck loading. The laboratory-based resilient modulus values were determined using a combination of test results on remolded and recompacted WesTrack materials and the KENLAYER computer program to estimate the modulus under the state of stress created by the FWD during testing. The results of this investigation continue to support the suspicion that significant differences do exist between resilient moduli determined from backcalculation and those determined through laboratory testing. Accordingly, some general observations are made concerning possible improvements in each methodology and concerning which of the two methodologies is better suited for a thorough pavement evaluation and design process. Overall, a better understanding of the problems associated with accurately characterizing pavement support under in-situ conditions is presented.
Strain Responses of Granular Base Materials in Stress Path Cyclic Triaxial Testing
Authors: Lo S.-C. R. , Chen K.
Published: April 2007

The responses of three granular base materials were studied by stress path cyclic triaxial (SPCT) tests. These tests were cyclic triaxial tests along constant stress increment ratio paths where the radial stress was cycled simultaneously and in phase with the axial stress. SPCT tests can better simulate the stress changes experienced by typical elements of granular base materials in a pavement system during a wheel pass. The stress increment ratio ( r), defined as the ratio of change in radial stress to change in axial stress, has a significant influence on the strain responses during cyclic loading. A parameter referred to as the proximity index was found to be most important in influencing the behavior pattern during cyclic loading. Provided the value of the proximity index is less than 0.7, the strain responses can be adequately modeled by a cross-anisotropic elastic model. However, the elastic stiffness parameters were correlated to both the number of loading cycles and the mean stress level and did not take a unique value.
Numerical Application of Shakedown Theory to Pavements with Anisotropic Layer Properties
Authors: Boulbibane Mostapha , Weichert Dieter , Raad Lutfi
Published: April 2007

A general numerical method for shakedown of pavements with anisotropic soil layers can be a useful development. The proposed method can be used to calculate rigorous bound solutions for soils whose cohesion varies with direction. To achieve this objective, the conventional isotropic Mohr-Coulomb yield criterion was generalized to include the effect of anisotropy, which is caused by the variation of cohesion with direction. The numerical formulation of the lower bound theorem using the modified anisotropic yield criterion was then developed. It was found that by using a suitable linear approximation of the yield surface, the application of the bound theorem led to a linear programming problem. The proposed numerical method was applied in the analysis of full-depth asphalt concrete pavements overlying clay subgrade. The analyses were conducted for different asphalt concrete temperatures and nonlinear stress-dependent subgrade properties. Results were compared for isotropic and anisotropic shear-strength parameters.
Synthesis and Literature Review of Nonwoven Paving Fabrics Performance in Overlays
Authors: Carmichael R. F. (FRANK) , Marienfeld Mark L.
Published: April 2007

Nonwoven paving fabrics have been used in asphalt overlays for more than three decades. Even though these nonwoven fabrics have been widely and successfully used in a variety of design and construction situations, there is no synthesis of their performance. In addition, current pavement structural-design methods do not provide a rational basis for considering the benefits of including paving fabrics in a pavement structural-section design. These two factors—limited performance data and lack of a design approach—have restricted the consideration and application of paving fabrics. These same limitations also have resulted in a lack of consistent consideration of the paving-fabric option in pavement management systems. The available literature on the uses and effectiveness of paving fabrics is synthesized. The information is based on a literature survey of more than 200 references conducted during the last 2 years to establish the benefits of using paving fabrics in pavement overlays as well as to acknowledge the results and findings of past successes and failures. After the literature review, a telephone survey of experienced users was conducted to determine the basic performance of nonwoven fabrics in asphalt-concrete-overlay performance. A synthesis of current practices and results is presented.
Simplified Method for Shear Design Based on AASHTO Load and Resistance Factor Design Specifications
Authors: Ma Zhongguo (JOHN) , Tadros Maher K.
Published: April 2007

Determination of the shear strength of prestressed concrete beams has become complicated in recent years. Much of the complexity comes from determining the concrete contribution ( Vc) to the overall shear resistance. Because of the empirical nature of the calculation of Vc by various codes and specifications and because of the insignificant cost impact of shear reinforcement, this complexity is not warranted. A simplified shear design method is proposed. A detailed example is presented to demonstrate a design that is based on the current AASHTO Load and Resistance Factor Design (LRFD) Specifications and the proposed method. An important issue in the shear design of thin-web, precast-prestressed concrete members is the maximum allowed shear reinforcement. AASHTO Standard Specifications require that Vs not exceed 0.66 [Formula: see text] ([Formula: see text] in MPa) or 8 [Formula: see text] ([Formula: see text] in psi). This limit has become a controlling design factor when wide-beam spacing and high-performance concrete are used. It is almost always a controlling parameter in the design of posttensioned I-beams. Recent experiments have shown that ( a) the AASHTO Standard Specifications limit is too conservative, and ( b) the limit of 0.25([Formula: see text]) on Vc + Vs in the AASHTO LRFD Specifications can be reached if adequate anchorage of the prestressing steel at member ends is provided. A summary of the full-scale test results is presented.
Fatigue Testing of Double-Angle Connections of Steel Railroad Bridges
Authors: Abouelmaaty Waled , Maragakis Emmanuel , Itani Ahmad , Douglas Bruce
Published: April 2007

An experimental study to evaluate the fatigue strength of double-angle connections used to connect stringers to floor beams in steel railroad bridges is described. The tests examined connections that could be used for either new construction or replacement of old, damaged connections. Double-angle connections are always assumed to be subjected only to shear stresses. But, in reality, some bending moment also is developed by this type of connection, causing additional flexural stresses, which, in turn, can produce fatigue damage by exceeding the constant amplitude fatigue limit. The amount of the transferred moment was estimated in the tests. Two full-scale specimens were built, representing the stringer-to-floor beam connection of a one-span, open-deck, through-plate girder bridge located in Nevada, typical of construction in the early 1900s. The specimens were tested under a cyclic loading of ± 195.8 kN, representing the equivalent load, which produces a total maximum shear reaction at the connection equal to the one produced in the actual bridge. However, the load cycles were from 0 to 391.6 kN in real bridges. The specimens also were tested beyond the fatigue initiation to observe the crack-propagation patterns and their growth rate. The tested specimens were modeled by the finite element program ADINA, and a comparison between the analytical and experimental results was made.
Subjective and Objective Evaluations of Bridge Damage
Authors: Lenett Michael S. , Griessmann Ann , Helmicki Arthur J. , Emin Aktan A.
Published: April 2007

A decommissioned, 40+-year-old reinforced concrete deck on a steel girder bridge was subjected to a series of induced damages, nondestructive field tests, and visual evaluations to compare objective and subjective methods of bridge-condition assessment. Prior subjective evaluations of bridge condition often produced highly variable results. For example, inspectors with different backgrounds and field experience disagreed on how severely certain forms of deterioration and damage influenced bridge behavior and safety so, consequently, different assessments of bridge condition were generated. Furthermore, a load rating of the “as-is” state of the bridge (e.g., the state before any induced damages), according to current Ohio Department of Transportation procedures, indicated that the bridge could only support truckloads of 227 804 N (51,192 lbf). However, the objective data acquired during nondestructive field testing of the bridge, which was subjected to truckloads of 282 130 N (63,400 lbf), revealed maximum superstructure deflections and live-load stresses of 0.190 cm (0.075 in.) and 15 985 kPa (2,320 psi)—values well within AASHTO limits. These values also imply that the bridge can support loads much greater than those indicated in the load rating. Comparing subjective and objective assessments for the induced damage scenarios yielded similar results. Essentially, data revealed that subjective methods of bridge evaluation and assessment were unable to properly characterize intrinsic bridge mechanisms and the influence that such mechanisms have on bridge behavior. Condition assessment of a typical reinforced concrete deck on a steel girder bridge should therefore include objective evaluations of bridge condition and behavior.
Cracking of Concrete Decks and Other Problems with Integral-Type Bridges
Authors: Burke Martin P.
Published: April 2007

During the continuing evolution of integral and semi-integral bridges, some problems have been encountered by engineers not familiar with the peculiarities of these structures, or with standard bridge practices that have been developed over many decades for the achievement of trouble-free bridge construction. Problems that occasionally confront transportation engineers include early-age cracking of concrete bridge decks; erosion of roadway shoulders, embankments, and backfill adjacent to bridge abutments; casting connections between moving members; and stage construction errors. Those aspects of integral-type bridge construction that deserve particular care and attention are examined and discussed. Presumably, a better awareness of such background will aid transportation engineers to achieve the economy, quality, and outstanding durability that integral-type bridges make possible.
Long-Term Performance of Elastomeric Bridge Bearings
Authors: Doody Michael E. , Noonan James E.
Published: April 2007

The effects of long-term service on bridge bearings composed of steel plates laminated between elastomeric layers, as placed on twin structures carrying the Route 400 Aurora Expressway over Route 16 and Conrail tracks in New York’s Erie County, are summarized. Expansion-joint bearings replaced as part of a recent rehabilitation project were recovered for evaluation and were found to be in generally good condition. New York’s current accelerated aging test procedures were evaluated by comparing mean ratings for these bearings (after simulated aging in their original 1969 acceptance testing) with results of similar tests conducted from 1992 to 1995 (after their removal from these bridges). An analysis of mean ratings from other 1969 acceptance tests is included, with similar tests repeated to determine the effects of the years in service. As a final step, the recovered bearings underwent further testing for conformance with other current specifications. The bearings, as originally installed on these structures, had problematic design, construction, and material properties, but nevertheless performed very well in service and were insensitive to these deficiencies.
Evaluation of Analysis Methods for Assessing Seismic Response
Authors: Yu Y. , Symans M.D. , Mclean D.I. , Cofer W.F.
Published: April 2007

Several analytical tools are available for assessing the seismic vulnerability of existing bridges. Each approach incorporates different assumptions and varies in complexity of application. As a result, selection of the most appropriate method for a given situation is often not clear. To aid in the selection process, four analysis methods for assessing seismic response are evaluated: linear elastic analysis, inelastic pushover analysis, capacity spectrum analysis, and nonlinear dynamic time history analysis. The four analysis methods are used in a limited study to determine the seismic response of two existing highway bridges under three different seismic ground motion conditions. The results of the analyses are used to evaluate the advantages, limitations, and ease of application of each approach for seismic analysis. Each method is shown to have merits and deficiencies that should be considered when selecting a seismic assessment method for a particular bridge structure.
Why the AASHTO Load and Resistance Factor Design Specifications?
Authors: Myint Lwin M.
Published: April 2007

The use of the new AASHTO Load and Resistance Factor Design (LRFD) Bridge Design Specifications offers many advantages. Major changes to and benefits of these specifications are discussed. The AASHTO LRFD is based on new developments in bridge engineering, sound principles, and logical approaches to ensure constructibility, safety, serviceability, inspectability, economy, and aesthetics. LRFD incorporates the best of working stress design and load factor design familiar to practicing bridge engineers. It is a comprehensive, well-organized, and practical specification, with commentary to provide explanation and background information. New bridges designed according to LRFD have the inherent advantage of a more uniform level of safety, resulting in low life-cycle cost. LRFD allows the use of advanced methods in design and analysis. It provides flexibility for maintaining good and successful engineering practices or customizing load and resistance factors to meet the demands of a project. There are many good reasons and motivations to use LRFD. College classes, training courses, design examples, workshops, and computer software are now available to ease the implementation of AASHTO LRFD.
Prediction of Driving Performance Through Computerized Testing: High-Risk-Driver Assessment and Training
Authors: Mills Kenneth C. , Parkman Katherine M. , Allen Smith G. , Rosendahl Fred
Published: April 2007

Two 10-min computerized cognitive tests were administered to a class of 35 male North Carolina Highway Patrol cadets at the beginning of driver training. The test (performance on-line) measured scanning and divided-attention skills, including indexes of visual and cognitive tunnel vision. Five months later the cadets were given 2 weeks of intensive driver training on the track in precision cone maneuvers and skid control and a final exam in high-speed pursuit. Relationships were examined between cognitive test scores and the track ratings of experienced driving instructors. The results showed that divided-attention deficits indicating tunnel vision predicted the lack of cadets’ skills on the track final exam in high-speed pursuit. When the top and bottom 25th percentile of the cadets’ high-speed pursuit scores were used as the criteria, the differences between the groups for divided-attention responses to displays at the center of a 38-cm (15-in.) computer monitor were not significant. However, the differences between the groups were significant for divided-attention responses at the outer edges of the display, indicating cognitive tunnel vision for the lower 25 percent of drivers. Thus, the more difficult divided-attention test requirements were more likely to select good drivers on complex driving skills. In addition, the cadets who had an advantage in decision-making skills continued to improve on that advantage as training continued. The first two cadets to crash on the road in the first year after training were in the bottom 15th percentile for divided-attention test scores. Implications for driver assessment and training are discussed.
Effects of Weather-Controlled Variable Speed Limits and Warning Signs on Driver Behavior
Authors: Rämä Pirkko
Published: April 2007

This study was designed to investigate the effects of weather-controlled speed limits and signs for slippery road conditions on driver behavior on the Finnish E18 test site. Local weather and road conditions were monitored from two unmanned road weather stations. The speed limits were lowered automatically during adverse road conditions, and in some cases signs for slippery road conditions were displayed as well. Speed and headway data were obtained from loop detectors. The results showed that in winter the change of the posted speed limit from 100 km/h to 80 km/h decreased the mean speed of cars traveling in free-flow traffic by 3.4 km/h, in addition to the average mean speed reduction of 6.3 km/h caused by adverse weather and road surface conditions. When poor road conditions were difficult to detect (e.g., there was no rain or snowfall or the rain was insignificant), the effect was 1.9 km/h higher (i.e., the reduction was 5.3 km/h). When road conditions were such that signs for slippery road conditions were also displayed, the variable speed limit system reduced the mean speed by 1.8 km/h, whereas the reduction caused by the weather was 9.3 km/h. In addition to the effects on mean speed, lowering of the speed limit decreased the speed variance. There was no remarkable effect on headways. The signs decreased speeds also on the road section next to the equipped section. The main implication of the study is that the system improved traffic safety by decreasing mean speeds and speed deviation.
Evaluating Networkwide Effects of Variable Message Signs in the Netherlands
Authors: Kraan Marëtte , van der Zijpp Nanne , Tutert Bas , Vonk Tanja , van Megen Dorry
Published: April 2007

The use of variable message signs (VMSs) is generally considered to be a powerful tool to influence route choice so as to increase safety and comfort during driving and improve network performance and to make optimum use of available capacity. Assessing whether such effects actually occur when VMSs are installed is a difficult task. This paper summarizes an extensive evaluation study carried out on the installation of 14 new VMSs on the Amsterdam orbital motorway. The study involves a number of issues. First, a networkwide analysis of aggregate performance indicators, such as traffic performance, severity of congestion, and travel time delay, is included. Second, the relation between the messages displayed on the VMS and the travel times experienced by drivers is analyzed. Finally, a stimulus-response analysis to find out how drivers actually respond to the messages is described. The study showed that the use of VMSs has a positive impact on network performance in the Amsterdam freeway system. Total congestion has decreased, and traffic performance has increased. Variation in congestion has decreased as well as variation in average travel speed. This finding implies that travel time has become more reliable and that the traffic flow is more homogeneous. The technical assessment showed that the displayed queue lengths, if interpreted correctly by drivers, are a good measure for expected delay. User response analysis showed that information has a significant effect on route choice. In general, the VMSs were found to improve the efficiency and reliability of the freeway system.
Road Curve Evaluation Based on Road View Perception Study
Authors: Zakowska Lidia
Published: April 2007

The main objective of the research was to investigate the perception of road curves, which is related directly to road safety, and in particular to test two experimental research methods used for road view evaluation and to evaluate the effect of visual information from static and dynamic road views on drivers’ perception of road curves. An experimental laboratory method of perceptual property evaluation for both static and dynamic road visualization techniques was designed and tested. The main conclusion is that the degree of simplification of the method is not directly proportional to the accuracy of the results. The major results of this experiment concern curve perception, which is a crucial design element according to existing theory. Based both on still pictures and on motion road views, this experiment shows that drivers are able to discriminate different levels of curvature and angle of curves and that perception of curvature is more sensitive to geometric curve properties for a dynamic presentation than for a static presentation. The degree of complexity of these effects is expressed in the significance of multifactorial interactions.
Reexamination of Roadside Encroachment Data
Authors: McGinnis Richard G.
Published: April 2007

Concerns about the Hutchinson and Kennedy (H&K) encroachment data used as the basis for AASHTO’s Roadside Design Guide (RDG) procedures for computing guardrail runout length have led to proposed revised guidelines based on more recent data collected by Cooper in Canada. The revised guidelines result in guardrail lengths that are approximately 35 percent shorter. Data from the original H&K and Cooper studies were analyzed to determine why the two studies seem to have inconsistent findings. The concerns about the H&K data expressed by the authors who proposed the revised guidelines were found to be invalid. However, team-by-team comparisons of the Cooper data revealed inconsistencies in encroachment rates, lengths, and departure angles for highways with similar speed limits. Documented data collection problems and unanswerable questions about the methodology used to measure encroachment lengths and departure angles make it impossible to validate the accuracy of the Cooper data. Adjustments were made to the Cooper data to compensate for possible data irregularities to examine the consistency between them and the H&K data. No evidence indicating that the encroachment lengths reported by H&K are inconsistently high compared with the encroachment lengths reported by Cooper was found. The findings suggest that reducing guardrail runout lengths from current RDG guidelines for highways with high speed limits [112 km/h (70 mph)] may not be prudent.
Using LS-DYNA Simulation To Solve a Design Problem: Bullnose Guardrail Example
Authors: Reid John D. , Bielenberg Bob W.
Published: April 2007

A bullnose median barrier was designed and successfully crash tested head-on at 100 km/h with a 2000-kg pickup truck. After a failed pickup truck test, LS-DYNA was used to simulate the failed system, to determine the cause of the failure, and to evaluate a solution to the problem. Subsequent testing substantiated the LS-DYNA predictions. To keep up with the design project deadlines, some features of the simulation model were simplified. For other features, however, great attention to detail was required to make a useful model. Specifically, a considerable amount of effort went into defining the material failure criteria and appropriate mesh density for the guardrail, rolling tires for the truck model, and application of the relatively new cable element in LS-DYNA. The simulation effort is documented to demonstrate how LS-DYNA can be used to solve difficult design problems in roadside safety applications.
Two-Dimensional Modeling of Collision Dynamics of Deflecting Concrete Barriers
Authors: Thomson Robert , Romilly Douglas , Navin Frank
Published: April 2007

Freestanding concrete highway barriers were originally implemented for work-zone applications. These barriers are becoming more widespread in their use and have been implemented in some innovative counter-flow applications. As the amount of freestanding barriers increases, so does the demand for detailed operational performance data. However, investigations of their crash protection and operation have been limited compared with those for the more common post-and-beam guardrail configurations. Computer simulation is one method for evaluating the performance of freestanding concrete barriers during vehicle collisions. A two-dimensional model of vehicle and barrier dynamics was developed to investigate the concrete barrier systems used by the British Columbia Ministry of Transportation and Highways. The simulation program was developed by using a multibody formulation for the barrier segments. A description of the model formulation is presented with a comparison of model output of recorded crash test data.
Resource Sharing: Wireless Telecommunications Site Lease Rates
Authors: Lindly Jay K.
Published: April 2007

“Resource sharing” refers to projects that use public right-of-way for telecommunications facilities and that result in some form of compensation to the public agency. The facilities most often installed are transmitter antennas supported on aboveground structures (wireless facilities) or buried fiber-optic cable. Research indicates that fewer than 10 state departments of transportation (DOTs) are leasing or licensing wireless sites to telecommunication companies, but many more states desire data concerning the revenue that they might receive from such installations. The current range of fees that state DOTs receive from the telecommunications companies for the wireless sites, and the fees that the DOTs receive from other companies (colocators) that place their facilities on a structure owned by a first locator, are described. The typical site locations, the group (DOT versus company) that identifies lease sites, typical support structures for the antennas, the manner in which the revenue may be used in the various states, and legal difficulties associated with wireless resource sharing are also described.
Connecting Minnesota: Superhighways to Information Superhighways
Authors: Lari Adeel Z. , Buckeye Kenneth R. , Helbach Mary L.
Published: April 2007

Facilitation of the development of the information superhighway, which is supported by fiber-optic technology, has begun to emerge on the agendas of some transportation agencies as they search for means to satisfy communications needs, create greater efficiencies and economic benefits, and possibly stem the trend toward increasing population concentrations in urban centers. In Minnesota, the state department of transportation has embarked on a process that has evolved into a landmark public-private partnership called Connecting Minnesota to build, operate, and maintain a high-speed, statewide fiber-optic communications backbone. When complete, nearly 75 percent of the state’s population will be within 16 km (10 mi) of this fiber-optic backbone. Many areas of rural Minnesota receive communications services via traditional copper wire or by limited lower-capacity fiber-optic cable. The current infrastructure does not meet the requirements for application of new and emerging technologies for the transfer of information between businesses, public agencies, educators, and friends and families. Access to advanced telecommunications technologies and services is necessary if outstate (remote) communities are to remain vital and prosperous. It has been suggested that in the next century the information superhighway will be as important to business and commerce as development of the railroads and the Interstate highway system was in the 19th and 20th centuries. Despite challenges, Connecting Minnesota and its partners are proceeding on a course for completion in 2001. Lessons learned from Minnesota’s experience should help smooth the road for other states attempting to facilitate and accelerate the construction of the information superhighway.
Infrastructure Inventory and Condition Assessment Using Airborne Laser Terrain Mapping and Digital Photography
Authors: Al-Turk E. , Uddin W.
Published: April 2007

The combination of airborne laser and digital camera technologies can be used as a cost-effective and efficient means of digital mapping for civil and environmental applications. A framework for the use of these remote-sensing technologies in conjunction with Global Positioning System (GPS) receivers for digital mapping of infrastructure projects is presented. An example of the benefit of airborne laser terrain mapping combined with differential positioning with a GPS is low-altitude, high-speed laser scanning of up to 81 km2 (20,000 acres) per day, which achieves an accuracy of 10 cm with reduced operating constraints, such as cloud and vegetation cover, traffic and usage, and time of day. The three-dimensional digital coordinate data are directly loaded into terrain mapping and computer-aided design software. This leads to efficient and error-free data processing and map generation. Conventional topographic surveys are slow, and aerial photogrammetry is limited by operating constraints and time-consuming data processing and interpretation. Examples of recent applications of the system for diverse projects like pipeline networks, power transmission lines, railroad tracks, and freeway interchanges are presented.
Some Experience with Geospatial Imagery and Route Optimization
Authors: Gipps Peter G. , Gu Kevin Q.
Published: April 2007

The means by which three technologies, geospatial imaging, soft-copy photogrammetry, and alignment optimization, can assist in generating and evaluating plans for new road alignments are assessed. The technologies are illustrated by two case studies. One, based on satellite data, was selected as a case study of the technologies because planning had been in progress for several years and all the data except the satellite images were available. The study was conducted at a broad level to demonstrate the ability of the technologies to produce high-quality results quickly and to prepare material for presentation. Constraints were kept simple because the aim was to demonstrate the technology, not to undertake a detailed study of the options; and the road authority’s costs for earthwork and other construction were used to provide comparability with the ongoing study. The costs of the alignments produced by the optimization were about 25 percent less than those from the ongoing study, and there was a consensus that the combination of technologies could have cut 12 to 18 months off the planning process. The second study, based on aerial photography, was a straight application of the technologies with no comparison with other studies and had to provide all the detail required for public presentations. It was a full-scale planning study in which aerial photography and alignment optimization technologies were used to identify the best transport corridors, to generate a set of low-cost alignment options within the corridors, and to assess the various alignment options.