bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation Modeling of Route Guidance Concept
Authors: Vandebona U. , Upadhyay P. K.
Published: April 2007

The methodology of a simulation model developed at the University of New South Wales, Australia, for the evaluation of performance of Dynamic Route Guidance Systems (DRGS) is described. The microscopic simulation model adopts the event update simulation method and allows assessment of route guidance performance under different scenarios such as varying levels of participation in guidance technologies and different intensities of travel demand. This research is important for marketing, costing, and introducing route guidance and can assist planners in identifying suitable networks and traffic conditions for such systems. The example application investigates selected operating scenarios of intersection delay conditions under different compositions of participation rates in route guidance. Preliminary investigations indicate that the effectiveness of route guidance is related to the level of intersection delays. An interesting outcome of this application is the identification that in networks with intersection delays which vary with time, those motorists without guidance assistance strive to make better forecasts of travel time in order to assist their route selection. At low levels of intersection delays, some motorists appear to make more than one nonoptimal route selection.
Personal Travel Assistants and the World Wide Web
Authors: Padmos Jeremy , Bernstein David
Published: April 2007

To be successful, handheld computers known as Personal Travel Assistants (PTAs) must be connected to external information sources. The viability of using the Internet and the world wide web (www) as such sources is explored. Considerations include whether www is flexible and robust enough to support various travel applications, whether to use a simulated passenger transportation terminal, and whether existing Internet protocols would be appropriate for PTAs.
Self-Selection Bias in Driver Performance Studies
Authors: Zhou Min , Lyles Richard W.
Published: April 2007

It is generally understood that there is some bias involved in selection of participants for driver performance studies, but little is known about the extent of this problem. To execute a National Cooperative Highway Research Program project on the effectiveness of traffic control devices, a sample of younger and older drivers was required. The purpose was to gain insight into the bias introduced through participant selection and self-selection. Of interest is whether the drivers who participate in projects for which driving or other testing is required tend to be different than the general population of licensed drivers. Results indicate that, compared with nonparticipants, participants are more active, more likely to travel and drive, less likely to avoid driving in certain circumstances, and less likely to have vision problems. The implication is that project participants represent more highly mobile and confident drivers than would be found in a random sample of the general population. However, project participants also had higher percentages of total accidents and violation points and were involved in more severe accidents than nonparticipants. These problems may be somewhat mitigated, though, by higher driving exposure for participant drivers. Such self-selection bias needs to be considered whenever research like this is undertaken.
Geographic Information Systems for Tracking Bridge Component Inspection and Repairs
Authors: Thierrin Raymond D.
Published: April 2007

Bridge component inspection and repair information has been traditionally collected on paper forms by field personnel and stored in project files. Because of the industrywide use of computer-aided design and drafting technology in bridge rehabilitation design, digital information for bridge components is often available as a by-product of the design process. In addition, projects are becoming more sophisticated and, as a result, the construction field office is becoming more automated. It is now possible to automate field data collection and management procedures so that information can be captured in a digital format in the field and used throughout the construction documentation process. The available technology includes pen-based computers, pen-enabled database software, and digital color cameras, all of which can be integrated into systems that are easily used by field inspection personnel. By using databases and geographic information systems, inspectors and engineers can readily review component information and track the progress of repairs for large-scale rehabilitation projects.
Quantifying the Effect of Pavement Performance Characteristics Using Partial Derivatives
Authors: Noureldin A. Samy
Published: April 2007

Asphalt content, aggregate characteristics, pavement layer thickness and degree of compaction, and initial pavement smoothness are keys to quality control in asphalt pavement construction. These measurable items are routinely checked during the construction process. The overall pavement performance life may be significantly affected when the specified characteristics of those items are not achieved in situ. Quantification of their effect on pavement performance is essential for quality roadway construction and rational pay adjustment factors. An approach is presented for estimating the expected loss (or gain) in pavement performance life resulting from any in situ deviation in performance-related characteristics from their specified values. The estimation is a simple exercise in the application of mathematical partial derivatives.
Constructability: A Quality Improvement Approach to Transportation Projects
Authors: Gambatese John A. , McManus James F.
Published: April 2007

Pressures to develop transportation projects that are biddable, buildable, and maintainable may be greater today than ever before. As a result, many transportation agencies are concerned about the constructability and quality of design documents for roadway facilities. The Washington State Department of Transportation has performed a research study to develop a constructability review process (CRP) to improve the constructability of its projects. The CRP is composed of constructability reviews at various prescribed points in the project time line. The reviews incorporate constructability checklists and planned meetings among all of the disciplines involved. Implementation of the CRP is expected to reduce the number of construction change orders, the total cost of change orders, construction and maintenance staff, and the amount of resources and to lead to a “zero addendum” bid phase.
Comparison of Tolling Strategies for Highway 407 in the Greater Toronto Area
Authors: Mekky Ali
Published: April 2007

Tolling strategies recently tested for Highway 407 in the Greater Toronto Area (GTA) are described and analyzed. The GTA is one of the fastest-growing urban areas in North America, with a population of about 5 million. Highway 407, a six-/four-lane freeway in the GTA, has been considered for many years as a relief for Highway 401. It is the busiest highway in North America and is used by more than 1 million vehicles per day. Highway 407 is being planned and constructed as a toll highway. Four strategies are compared. In the base strategy, the toll rate per kilometer is fixed and the value of the toll paid depends on the distance traveled on the highway. In Strategy 2, vehicles on Highway 407 are tolled on the entrance ramps as well as at some points on the highway (main “virtual” plazas). In Strategies 3 and 4, each driver has two choices. The first is to pay a toll depending on the distance traveled. The second is to pay a certain fixed toll once the driver crosses certain points on the highway (mainline plazas) and on the exit ramps. The strategies are compared from the points of view of the number of users, the vehicle-kilometers on the highway, the revenues, and the average toll paid. The GTA mathematical model, within the EMME/2 environment, is used. The mathematical model and the evaluation process are described.
Guidelines for Right-Turn Treatments at Unsignalized Intersections and Driveways on Rural Highways
Authors: Hasan Tanweer , Stokes Robert W.
Published: April 2007

Guidelines for right-turn treatments at unsignalized intersections and driveways on rural two-lane and four-lane highways are presented. Two types of treatments, full-width lane and taper, were considered over the do-nothing radius treatment. The guidelines indicate the design hourly traffic volumes for which the benefits of right-turn treatments exceed their costs. The benefits used in the economic analysis were the operational and accident cost savings provided by right-turn treatments. The costs used in the development of the guidelines were the costs of constructing full-width right-turn lanes and tapers. The operational effects were estimated in terms of delay and excess fuel consumption experienced by through traffic due to right-turning vehicles. To account for the safety effects, the relationship between speed differential and accidents was used to estimate the reduction in right-turn, same-direction, rear-end accidents that would be expected to result from the provision of a right-turn treatment. The guidelines indicate the right-turn design hourly volume required to justify a right-turn treatment as a function of the following factors: ( a) directional design hourly volume, (b) highway operating speed, and ( c) number of lanes on the highway. Comparisons with other guidelines indicate that the range of guidelines developed are reasonable. In addition, they are more definitive than other guidelines because they account for highway operating speed and address taper treatments as well as full-width turn lanes.
Formal Observational Approach to Staged Loading
Authors: Baecher Gregory B. , Ladd Charles C.
Published: April 2007

Construction of a major industrial facility on soft clay was accomplished by staged loading to consolidate and thus increase the strength of foundation soils before the complete final load was applied. Extensive in situ and laboratory testing allowed a formal observational approach to be used, in which uncertainty analysis of the preliminary design was combined with field monitoring data to update soil parameter and site condition estimates. Traditional Bayesian methods were used to modify initial estimates and thus to update predictions of facility performance in the later stages of construction.
Uncertainty Analysis of Tunnel Roof Stability
Authors: Mauldon Matthew , Chou Karen C. , Wu Yan
Published: April 2007

Fractures, joints, and other discontinuities significantly influence the stability of excavations in rock. Unstable blocks of rock in the roofs of tunnels can have a significant effect on the safety and economic feasibility of highways and railroads. The stability of tunnel roof keyblocks subject to self-weight and surface forces is examined using linear programming methods. An instability measure based on the concept of fuzzy sets is used to characterize the level of instability. On the basis of analysis of the instability measure, the support pressure required to stabilize the tunnel roof can be estimated. A probabilistic analysis based on the expectation of the instability measure is used to examine the effect of the uncertainties caused by the variability of rock material properties.
Characteristics of Typical Minnesota Aggregates
Authors: Stroup-Gardiner M. , Newcomb D. , Kussman W. , Olson Roger
Published: April 2007

The consensus aggregate properties recommended in SUPERPAVE and selected mixture properties were evaluated for a wide range of Minnesota aggregate sources obtained from 16 construction projects completed in 1993. Measured aggregate properties included the sand equivalent (SE) and fine aggregate angularity for the fine aggregate fractions, and percentage of fractured faces and flat and elongated particles in the coarse aggregate fractions. Laboratory-compacted samples were prepared and tested to determine air voids, voids in mineral aggregate (VMA), tensile strengths, and an assessment of the moisture sensitivity of the mixtures. Only 3 of 29 SE values for individual stockpiles were less than 40 percent. These values were not significantly affected by changes in either the general mineralogy (i.e., igneous, limestone, mixed) or the percentage passing the 0.075-mm (No. 200) sieve. Single regression analyses indicated no significant relationship between SE and either mixture moisture sensitivity or VMA. While all 25 stockpiles tested had fine aggregate angularity values greater than 40, 9 stockpiles had values below 45. It was suggested that since Minnesota aggregate gradations commonly pass through the SUPERPAVE re-stricted zone (one purpose of which is to limit the use of rounded natural sands), the minimum fine aggregate angularity value be set at 45 for all mixtures to preclude the use of 100 percent natural sands. A significant number of Minnesota coarse aggregate stockpiles have a moderate to high content of flat particles (20 to 50 percent).
Method To Ensure Stone-on-Stone Contact in Stone Matrix Asphalt Paving Mixtures
Authors: Brown E. R. , Haddock John E.
Published: April 2007

The use of stone matrix asphalt (SMA) has continued to rise in the United States because of its ability to withstand heavy traffic without rutting. This ability is derived from a stone-on-stone coarse aggregate skeleton. While this coarse aggregate skeleton is imperative for SMA to perform, no quantitative method exists to measure it. A method for determining when stone-on-stone contact exists is presented. The proposed method first determines the voids in the coarse aggregate (VCA) for the coarse aggregate–only fraction of the SMA mixture. Second, the VCA is determined for the entire SMA mixture. When the two VCA values are compared, the VCA of the SMA mixture should be less than or equal to the VCA of the coarse aggregate–only fraction to ensure that stone-on-stone contact exists in the mixture. Five different methods for determining the VCA of the coarse aggregate–only fraction were used to see which performed best and was the most practical. The aggregate degradation produced by each of the five methods was also determined and compared with the coarse aggregate breakdown produced in an SMA mixture compacted with 50 blows of a Marshall hammer. The results indicate that the Superpave gyratory compactor and dry-rodded methods produced the best results. Both methods are recommended for further testing.
Three-Dimensional Nonlinear Stability Analysis of Tangent Continuous Welded Rail Track Under Temperature and Mechanical Loads
Authors: Bao Yulin , Barenberg Ernest J.
Published: April 2007

Results from applications of the three-dimensional continuous welded rail (CWR) track model ILLIBUCKLE to a tangent CWR track with nonlinear resistance and lateral geometric imperfections are presented. Stability analysis is made of the tracks under temperature and mechanical loads by using temperature lateral-displacement curves. Tangent CWR track stability is highly sensitive not only to ballast lateral resistance and geometric imperfections of the the initial track but also to the vertical rotational stiffness in rail-pad fastener systems and vehicle lateral loads. It is concluded that not only the peak values but also the initial slope and the limit resistance in the ballast lateral-resistance curve obtained from a single-tie push test are important in evaluation of track stability. With regard to vertical rotational stiffness in a rail-pad fastener system, track stability is not significantly affected by the nonlinearities, but it is affected by the initial slope. Effects of the combination of mechanical and thermal loads on tangent track stability are presented. The reduction of ballast lateral resistance due to the uplift of rail tie under vehicle vertical loads as well as the magnitude of vehicle lateral loads significantly decrease track stability. A 1400-kg vehicle lateral load can buckle tangent CWR track under a rail-temperature increase as low as 56°C (100°F) under unfavorable conditions.
Frictional Characteristics of Sand and Sand-Deicer Mixtures on Bare Ice
Authors: Hossain M. Makbul , Bajorski Peter , Yang Wei-Shih
Published: April 2007

Frictional characteristics of sand and sand-deicer mixtures were investigated as functions of temperature, gradation, and application rate. Results of a laboratory cold-room study in which sliding friction was measured with a British pendulum tester are described. Four temperatures, three sand gradations, four brine concentrations, and four sand-application rates were investigated. All tests were performed on an ice sheet in a cold room, where sand temperatures were maintained close to ice temperatures. Three categories of materials were tested: sand alone, sand-salt mixtures, and sand-brine mixtures. Results showed that sand-brine mixtures outperformed the other two, with significantly greater sliding friction. Two brine concentrations were found suitable in two temperature ranges. Below −12°C, 2.5 percent brine (by weight) gave good results with a fine sand (passing the No. 30 U.S. sieve but retained on the No. 50 sieve) at a sand application rate of 1 g over a test area of 100 × 200 mm, with a sand-to-brine ratio of 1:1 by weight. This rate is equivalent to field application of 183 kg of sand per lane-km. Friction was achieved by generating a bond between sand and ice by using a low-concentration brine (2.5 percent by weight). At temperatures above −12°C, satisfactory results also were obtained with 25 percent brine mixed with the same sand at a ratio of 2:1 by weight. In this case, friction was increased by roughening the ice surface with a higher-concentration brine (25 percent by weight).
Characterizing Asphalt Volatility
Authors: Zupanick Michael , Baselice Valerie
Published: April 2007

Asphalt volatility is one of several factors that can affect the degree of environmental discharge and worker fume exposure that occurs during hot-mix manufacturing and construction. Fundamental volatility measurements using vapor pressure generally are not practical for asphalt because of its low volatility. Eight potential asphalt volatility tests were considered: thin film oven test, rolling thin film oven test, Cleveland open cup flash point, steam distillation, thermogravimetric analysis, German rotating flask test, vacuum flask distillation, and high-temperature simulated distillation by gas chromatography. Many of these tests are affected by testing artifacts such as oxygen addition, skin formation, and thermal degradation. The procedure, standardization, and validity of each test are discussed. Existing data are reviewed and new data are presented to demonstrate the relationships among these tests. On the basis of available information, it is concluded that the best empirical (condition-dependent) volatility test is the German rotating flask test conducted with an inert gas, and the best compositional (conditionindependent) volatility test is high-temperature simulated distillation by gas chromatography.
Willingness To Pay for Advanced Traveler Information Systems: SmarTraveler Case Study
Authors: Polydoropoulou Amalia , Gopinath Dinesh A. , Ben-Akiva Moshe
Published: April 2007

The issue of travelers' adoption of an advanced traveler information system (ATIS) and willingness to pay for such information services is addressed. A case study is presented of SmarTraveler, an ATIS that provides, via telephone, real-time location-specific traffic and transit information in the greater Boston area. The model is an integrated system of discrete choice and latent variable models. It predicts travelers' frequency of use and subscription under varying pricing scenarios. Two models are presented: one for current SmarTraveler users, and one for nonusers. The SmarTraveler usage rate is modeled as a function of payment method and pricing, travelers' travel and socioeconomic characteristics, and their attitudes and perceptions toward ATIS. The data used in model estimation included willingness-to-pay scenarios involving two methods of payment: a flat monthly fee, and a charge per call. It was found that for nonusers, the higher the expected benefit from an ATIS, the higher the willingness to pay. This expected benefit is a latent variable indicated via the importance placed by individuals on ATIS attributes such as reliability, relevance, and coverage. For users, the utility of SmarTraveler is affected strongly by the users' level of satisfaction with the service. A modeling framework is developed that captures response biases and presents figures on willingness to pay for an innovative ATIS actually implemented in the market.
Development of Temperature-Effect Model for Predicting Rutting of Asphalt Mixtures Using Georgia Loaded Wheel Tester
Authors: Shami Haroon I. , Lai James S. , D'Angelo John A. , Harman Thomas P.
Published: April 2007

Use of the Georgia loaded wheel tester (LWT) to evaluate rutting susceptibility of asphalt mixtures has gained acceptance by the asphalt paving industry. The test is typically conducted at 40°C for 8,000 cycles and the rut-depth value measured at the end of the test is compared with a maximum criteria of 5.0 mm or 7.5 mm to assess rutting susceptibility of the mixture. A temperature effect model (TEM) was developed using the LWT test data from seven asphalt mixtures. The TEM developed can be used to predict the rut-depth values of an asphalt mixture at different temperatures and number of loading cycles from the LWT performed on the asphalt mixture at one testing condition. The predicted rut-depth values from the TEM compared very closely with the measured values. For the five dense-graded hot-mix asphalt mixtures (HMA), only 7 out of 170 predicted rut-depth values deviated from the measured values by more than 0.8 mm. For the two stone-matrix asphalt mixtures (SMA), only 2 out of 64 predicted values deviated from the measured values by more than 0.8 mm. The TEM can be used to determine the equivalent rut-depth acceptance values at a lower number of rut-testing cycles, and thus can shorten the testing time for performing the LWT rutting susceptibility acceptance test. This can be useful for the field quality control of HMA. Using this predictive model, the LWT rutdepth acceptance criteria can be developed for asphalt mixtures at the temperatures more closely related to the actual pavement temperatures in the field.
Calibrating and Validating TRAF-NETSIM Model of Single-Point Urban Interchange
Authors: Dixon Michael P.
Published: April 2007

A model of a single-point urban interchange (SPUI) was calibrated and validated using the traffic simulation program (TRAF-NETSIM). The model was calibrated on the basis of field observations at several existing SPUIs, and the model was validated on the basis of measures of effectiveness at a prototype interchange. Statistical analyses of several parameters were performed to determine confidence intervals and decile distributions and to compare values and distributions with defaults provided in TRAF-NETSIM. Other parameters were verified by informal field observations at the prototype interchange. The validation of the model demonstrated that TRAF-NETSIM can adequately represent traffic operations at a SPUI. Observations regarding the SPUI will provide additional insight into SPUI traffic operational characteristics. The methodology used to calibrate and validate the model of the SPUI should also be applicable to other modeling applications, ensuring a realistic and accurate representation of traffic operational conditions in a transportation system.
Use of Pavement Management System Data For Pavement Engineering Applications
Authors: Gharaibeh Nasir , LaTorre Francesca , Darter Michael , Lippert David
Published: April 2007

Agencies have collected data for pavement management for many years now. These data have been used primarily to develop short- and long-range rehabilitation programs. Another valuable use of these data is improvements to engineering procedures. The Illinois Pavement Feedback System (IPFS) is a comprehensive inventory and monitoring system that was designed in 1984 to provide data for both programming and engineering uses. Over the past 10 years many engineering issues have been addressed through the use of these data. IPFS data were used to provide feedback to designers and administrators on the design of new (or original) pavements and on overlay designs. Results from a survival analysis of thousands of kilometers of original jointed reinforced concrete pavement (JRCP), continuously reinforced concrete pavement and hot-mix asphalt concrete pavements and asphalt concrete (AC) overlays of these pavements were used. Key results relate to performance variability (a wide range of performance was found for identical designs) and thus the need for a design reliability greater than 50 percent, the expected pavement in-service life in terms of both age and traffic [equivalent single axle loads (ESALs)] of each pavement type and overlays (for example, the mean life of JRCP was 24.1 years and 16.6 million ESALs and the mean life of the first thick AC overlay was 14.5 years and 23 million ESALs), the effect of overlay design thickness, and the effect of concrete material durability (D cracking reduced ESALs carried by 50 percent).
Algorithm for Determining Weight Factors of Pavement Distress Index
Authors: Chou Chia-Pei , Chang Chien-Yen
Published: April 2007

Distress is one of the primary measurements of pavement condition. Thus, in a pavement evaluation program, distress type, severity, and extent should be properly identified. A pavement distress index (PDI) may be calculated by mathematically combining the effects of distresses on pavement conditions. Before the calculation of PDI, each distress attribute must be assigned a weight factor and a severity factor. An analytical algorithm that converts the subjective rating values of distress attributes to a rational weighting scale that provides quantified measurements of the effects of each distress on pavement damage and riding quality is presented. A case study for applying this procedure to the pavements of roadway samples from the Highway Bureau and the National Freeway Bureau in Taiwan also is presented. Through the analysis procedure, it was found that pothole has the largest weight factor (100) and that longitudinal crack has the lowest (49). The severity factors vary from 0.24 to 1.00, depending on the distress type and severity level.
Global Positioning System with an Attitude: Method for Collecting Roadway Grade and Superelevation Data
Authors: Awuah-Baffour Robert , Sarasua Wayne , Dixon Karen K. , Bachman William , Guensler Randall
Published: April 2007

The use of a specialized Global Positioning System (GPS) to conduct high-speed surveys of roadway alignment, grade, and cross-slope characteristics is discussed. The system uses a single GPS receiver that has 24 channels monitoring four separate antennas (six channels each). The collection of attitude (heading, pitch, and roll) is made possible through the relative orientation of the antennas. By mounting the system on a road surveillance vehicle, accurate grades, superelevation, and crown measurements can be made without differentially correcting the GPS data. However, to gather precise positional data that correspond to the roadway measurements, differential correction with a GPS base station at a fixed known point is required. The design and use of this attitude GPS unit are addressed. Accuracy specifications for static testing are provided along with techniques to maximize this accuracy. Kinematic data collection is depicted for a local road and a freeway off-ramp. The use of digital terrain modeling technology provides a promising graphic database representation of the roadway characteristics.
Evolution of Fatigue-Resistant Steel Bridges
Authors: Fisher John W.
Published: April 2007

Fatigue cracking was seldom found in welded highway and railroad bridges from the time of their introduction in the 1950s until the late 1960s. The fatigue design specifications used in that era were developed from a limited knowledge base and largely with small-scale specimens that simulated welded details. During the AASHO Road Test in 1960 fatigue cracks were observed to develop in cover-plated steel bridge beams as a result of the heavy loads and high stress ranges. This observation subsequently resulted in a series of experimental studies supported by NCHRP starting in 1967. The laboratory studies with full-scale details were designed to evaluate the significance of many factors thought to influence fatigue resistance, including loading history (and associated stress states including residual stresses), type of steel, design details, and quality of fabrication. These studies indicated that small-scale specimens overestimated fatigue resistance and that only the stress range for a given detail was critical. As a result fatigue resistance design provisions in use since the 1950s were inadequate and overly optimistic, particularly at longer lives, because the assumption of a fatigue limit of 2 million cycles proved to be incorrect. The results of laboratory studies with full-size specimens and their impact on changing the concept of fatigue design and the bridge fatigue design provisions used for highway and railroad bridges today are reviewed. During the 1970s and 1980s fatigue cracking associated with low-fatigue-strength details (Categories E and E′), such as cover plates and lateral gusset plates, increased. Cracks were also found in transverse groove welds, particularly in attachments such as longitudinal stiffeners, gusset plates and even flange splices. These groove weld cracks generally occurred because large defects were inadvertently fabricated into the welded joint. The occurrence of these cracks was found to be predictable and in agreement with the laboratory fatigue resistance results. The 1970s also exposed an unexpected source of cracking due to the distortion of small web gaps that were frequently used in welded bridge structures. Web gap cracking continues to develop in a wide range of bridge types. It is the source of most fatigue cracks in steel bridges. Existing bridges that are susceptible to fatigue cracks or that develop fatigue cracks at primary details or from web gap distortion are easily repaired or retrofitted to ensure long-term performance. Examples of such repairs are reviewed. The future is bright for welded bridges because the knowledge base and current design provisions make it possible to design and build fatigue-resistant bridges.
Brush Creek Improvements: Double Cell Arch Culvert Installation in Prairie Village, Kansas
Authors: Carfagno Michael G. , Vaia Lynne A. , Evans Kristi
Published: April 2007

A double line of precast concrete, three-sided, arch culvert-bridge units that were used to enclose Brush Creek between two Kansas City, Missouri, suburbs is described. Two principal streets intersected on top of the structure. The contractor was allowed only 14 days to complete construction of the structure and reopen the intersection. The Brush Creek Improvements project in Prairie Village, Kansas, required 100 pieces of double-cell CON/SPAN precast culvert units with 6.10 m (20 ft) of span and 2.13 m (7 ft) of rise and 78 pieces of precast concrete footings. The design also featured an S-curve alignment.
Effects on Accidents of Automatic Speed Enforcement in Norway
Authors: Elvik Rune
Published: April 2007

Automatic speed enforcement by means of photo radar was introduced in Norway in 1988. The results of a before-and-after study of the effects of automatic speed enforcement on accidents are reported in this paper. The study controlled for general trends in the number of accidents and regression to the mean. A statistically significant reduction of 20 percent in the number of injury accidents was found. The number of property-damage-only accidents was reduced by 12 percent. This change was not statistically significant at the 5 percent level. The effect of automatic speed enforcement on the number of injury accidents varied according to the level of conformance with official warrants for its use. The warrants refer to accident rate (accidents per vehicle kilometer) and accident density (accidents per kilometer of road). A decline of 26 percent in injury accidents was found on road sections conforming with both warrants. On road sections not conforming with any of the warrants, injury accidents declined by 5 percent. The results of this study confirm the results of previous studies of the effects of automatic speed enforcement on accidents.
Effectiveness of Automated Speed-Monitoring Cameras in Kuwait
Authors: Ali S. Y. , Al-Saleh O. , Koushki P. A.
Published: April 2007

In 1994 the General Traffic Department installed automatic radar cameras to monitor traffic speed at a number of strategic roadway locations in Kuwait. The aim was to lower the number of high-speed violations and thus reduce road accidents. Recent traffic safety records point to an increase in both the number of violations and the occurrence of road accidents. It is argued in this paper that without live enforcement support and active follow-up of camera-recorded violations, the effectiveness of these cameras in improving road safety is insignificant at best, particularly in the undisciplined driving environment of the oil-rich nations in the Middle East. The speed of traffic was simultaneously measured via radar instruments both at the automatic camera site and at sections approximately 1 km before or after or before and after the cameras at eight camera locations. Measurements were recorded for six 1/2-hr periods at each site for a total of 72 hr over a period of 3 months, so that morning, afternoon, and after-dark hours, as well as different days of the week and roadway types, were covered. Analysis of the speed data showed that for the three daily periods and various roadway types, traffic speeds were consistently higher in sections before or after or before and after the automatic camera at the camera site. Statistical tests indicated that the difference in speed measured at and away from the cameras was at the 99 percent level. The findings demonstrate that in a traffic environment characterized by poor driving behavior, inconsistent and piecemeal driver education programs, and insufficient presence of law enforcement officials, reliance on automatic cameras alone to reduce traffic violations is doomed to fail.
Incidence of Large Truck-Passenger Vehicle Underride Crashes in Fatal Accident Reporting System and National Accident Sampling System
Authors: Braver Elisa R. , Cammisa Michael X. , Lund Adrian K. , Early Nancy , Mitter Eric L. , Powell Michael R.
Published: April 2007

Between 1988 and 1993, the Fatal Accident Reporting System (FARS) coded 4 percent of all fatal large truck–passenger vehicle crashes as involving underrides (portion of passenger vehicle slides under a large truck) or overrides (truck rides over another vehicle). In contrast, the National Accident Sampling System Crashworthiness Data System (NASS/CDS) coded 27 percent of a sample of 275 fatal large truck–passenger vehicle crashes as underrides during the same years. Seven percent of these 275 fatal crashes are identified as underrides in FARS. The discrepancy between FARS and NASS coding becomes more pronounced when underrides involving sides of passenger vehicles or trucks are considered. The reason for this discrepancy is that NASS/CDS did not code underrides involving side impacts, but FARS did. When underrides involving side impacts were added, the total percentage of underrides in NASS/CDS rose from 27 percent to 50 percent of fatal truck-car crashes. The most likely explanations for the lower incidence of underride coding in FARS are that (a) the greater amounts of information available to NASS/CDS analysts enable more complete identification of underrides, (b) FARS analysts sometimes may not recognize that an underride has occurred, and (c) underride was not a separate FARS variable before 1994. On the basis of NASS/CDS data, an estimated 1,108 fatal underride crashes occurred each year between 1988 and 1993 [95 percent confidence interval (CI) = 735, 1482]. Of these 1,108 underrides, 634 involved the front (CI = 328, 942), 248 involved the rear (CI = 137, 360), and 226 involved the sides (CI = 110, 341) of large trucks.
Stated-Preference Examination of Attitudes Toward Carpooling to Work in Calgary
Authors: Hunt J. D. , McMillan J. D. P.
Published: April 2007

A stated-preference experiment was performed in Calgary to examine the nature of various influences on the decision to carpool to work in the central business district. A total of 678 complete interviews were conducted. In each interview, the respondent was presented with five successive pairs of possible automobile use alternatives and asked to indicate which alternative was preferred in each case. This forced the respondent to trade off among conditions regarding specific attributes. Several socioeconomic characteristics of the respondent and attributes of the respondent's actual trip to work were also recorded, and the contents of the hypothetical alternatives presented were adjusted accordingly. The observations thus obtained were used to estimate the parameter values for different utility functions in logit models representing this choice of behavior. The results indicate, among other things, that the extra time spent in the automobile serving other carpool participants is valued at a premium rate of about $4.00 (Canadian) per hour (or about 45 percent) more than the automobile ride time for the direct trip; the availability of a guaranteed ride home has a value roughly equivalent to the basic transit fare in Calgary; and each additional household member in a carpool adds further benefit in a reasonably linear manner but does not alter the effect of parking costs for the respondent, whereas each additional non-household member does not add further benefit but does tend to reduce in a nonlinear manner the effect of parking costs for the respondent.
Development and Testing of Steel U-Channel Slip Safe Sign Support
Authors: Mauer Frederick , Bullard D. Lance , Alberson Dean C. , Menges Wanda L.
Published: April 2007

Researchers at Texas Transportation Institute designed a Slip Safe connection for use with steel U-channel sign-support structures within the highway right-of-way. The Slip Safe connection has two design configurations: a small Slip Safe design for single U-channel posts and a larger Slip Safe for back-to-back U-channel posts. Both configurations utilize Rib-Bak U-channel posts weighing up to 5.9 kg/m manufactured from 552-MPa yield billet steel. The Slip Safe is designed for use in a range of soil types with up to three supports per installation. There are two advantages of this Slip Safe design. First, the Slip Safe eliminates the dependency on material properties to achieve acceptable breakaway performance. In the past, all direct-driven and the majority of current breakaway designs for steel U-channel, square tube, wood, and round pipe sign supports have depended upon this. Second, the Slip Safe is omnidirectional and both hardware and supports are highly reusable due to the low energy required to activate the system. The Slip Safe designs are unlike most types of highway safety appurtenances in which performance is critically dependent on the failure of a bolt or bolts, the support material properties, or a combination of both. The Slip Safe has two advantages over other current U-channel connections. First, activation of the Slip Safe occurs with approximately one-third of the force needed to activate fracture-type connections. Second, the only disposable component in the Slip Safe connection is the keeper plate. All casting, bolts, and U-channel supports were undamaged, yielding economic advantages in high-frequency impact locations.
Interim Report on Colorado Scenic and Historic Byways Economic-Impact Study
Authors: Sem John , Goff Patrick , Pearce Sally
Published: April 2007

Despite the extensive use of highway designations to promote tourism, there has been little research on the economic effects of these efforts. An interim economic-impact study was conducted as an attempt to estimate the economic effects of Colorado Scenic and Historic Byway designation on tourism-related businesses in communities along the byway routes. The study's research strategies included a review of the literature and research on the economic impacts of travel and tourism, a byways traffic analysis, and a survey of community tourism businesses. The results indicated the economic significance of the travel and tourism industry, and more specifically of byway designation. The findings suggested that byway designation may have an effect on increased visitor traffic, visitor expenditures, and total retail sales in communities along the byway routes.
General Aviation User Benefits
Authors: Joshi Aparna S. , Hartgen David T.
Published: April 2007

A user benefits economic impact model of general aviation (GA) travel is developed using data for five publicly owned airports in North Carolina. A 1994 survey of GA users concerning flight origins, destinations, intermediate stops, and local expenditures is geographically represented with TransCAD 3.0, a geographic information system. Minimum-time road paths for these flights are also computed. User costs including passenger value of time, local ground transportation, overnight costs, and expenditures for crew and passengers are then estimated, and costs and travel times for the two modes are calculated for each airport. Findings are compared with the traditional jobs-based method of estimating airport impacts. Results indicate that as the passenger value of time increases, travel using the general aviation mode becomes more advantageous than is automobile travel. In addition, as the trip length increases, more time spent in traveling induces overnight stays and thus travel expenses rise considerably. However, uncertainty in user expenditures is large (±20 to 40 percent) for typical values of the key inputs. The study concludes that although the user benefits method of estimating aviation impacts is promising, more research is needed to refine the method for use in practice.
Survey and Determination of Historic Significance of Nonarched Concrete Bridges in Virginia Constructed Prior to 1950
Authors: Miller Ann B.
Published: April 2007

Bridges are a cultural resource that must be considered for historic significance under the Historic Preservation Act of 1966. The Virginia Transportation Research Council conducted pioneering studies of Virginia’s early metal truss bridges and concrete and masonry arch bridges during the 1970s and 1980s. However, no comprehensive evaluation of nonarched concrete bridges in Virginia had been undertaken, and it had become standard practice to evaluate these bridges on a case-by-case basis as projects arose that might affect them. Most of these studies were done by outside consultants, a time-consuming and expensive method. The Virginia Transportation Research Council’s Survey of Non-Arched Historic Concrete Bridges in Virginia Constructed Prior to 1950 has rectified the lack of information and analysis of these bridges (1950 was chosen as a cutoff date because structures generally must be at least 50 years old to be considered historically significant under National Register criteria). A field survey and data tabulation were completed, and criteria for the evaluation of historic significance were developed and applied to the results of the survey and analysis. Of 1,420 nonarched concrete bridges built before 1950, fewer than a dozen were found to be individually eligible for the National Register of Historic Places. The project identified Virginia’s few significant bridges of this type for appropriate management, and cleared more than 1,400 bridges, the great majority of Virginia’s nonarched concrete bridges, for maintenance and upgrade as needed. It is estimated that this project has already saved the Virginia Department of Transportation $500,000 and eliminated a typical 3- to 4-month delay for each project. Projected savings arising from this project are estimated at approximately $2.5 million over the next 10 years.
Environmental Accounting in Greater Vancouver Transportation System Planning
Authors: Bein Peter , Kawczynski Mike
Published: April 2007

Transportation facility and system options for the greater Vancouver region are evaluated using the provincial guidelines for full-cost accounting. The impact of the monetized environmental accounts on the overall evaluation is presented, using facility, system option, and pricing examples from the regional plan. Within project options that are homogeneous with respect to travel demand management or modal split, environmental account values do not differ much, just as in the user cost accounts. Monetized environmental account values are two to three times smaller than the user cost in project-level cases. At the system level, in which travel demand management and modal choice are among the principal objectives, environmental benefits are decisive, whereas user benefits may be inconclusive. The estimated monetized subsidy to full costs of the automobile underpricing of personal transport has increased from 20 percent to more than 50 percent with analytical advances since 1993. Serious intangible externalities remain unmonetized, but should nevertheless be considered. Limitations of transportation demand model and data (peak spreading, 24-hr operation, and determination of vehicle speeds) require remediation for accurate environmental accounting. Fuel consumption and vehicle operating costs at low levels of service, and impacts of travel demand management on travel behavior, are decisive for system appraisals. At the project level, queueing data, level of service, and capacity must be available. Speed-and vehicle-specific emission rates are also necessary for accurate accounting at the project and system levels.
Comparison of Vegetational, Hydrologic, and Edaphic Characteristics of Riverine Forested Wetlands on North Carolina Coastal Plain
Authors: Beissel Kelly D. , Shear Theodore H.
Published: April 2007

Although forested wetlands are relatively abundant on the coastal plain of North Carolina, restoration of forested wetlands is becoming more common since these communities are frequent targets for impact or destruction, especially as a result of road construction projects. Successful restoration of ecosystems is made difficult by a lack of basic knowledge about the soil and hydrologic characteristics of different types of forested wetlands. The plant community composition of two forested wetlands types is described: bottomland hardwood communities and a coastal plain small stream swamp. The edaphic and hydrologic characteristics of each community type were also compared. Many researchers have suggested the construction of detailed water budgets to describe the hydrologic regimes of natural forested wetlands and for use in restoration projects. Although several soil and hydrologic characteristics were associated with variation in plant community composition, the results of this investigation suggest that using a particular flood frequency as a surrogate measure of several flood frequencies may be sufficient to explain this variation. Use of this information would simplify the reconstruction of appropriate hydrologic regimes in forested wetlands and perhaps increase the success of restoration projects.