bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of a Relational Accident Database Management System for Mexican Federal Roads
Authors: Mendoza Alberto , Uribe Aristóteles , Gil Claudia Z. , Mayoral Emilio
Published: April 2007

Two years ago, the Mexican Transportation Institute began to develop a computer-based management system of the information collected by various organizations about accidents occurring on the Federal Road Network. This system combines the information gathered by these organizations with the purpose of completing and validating the data so that tools can be developed for processing and analyzing the validated data and the processed data and developed tools can be made available to users. It was decided to support the development of such efforts on computer databases already being generated, on database processing and management software, on geographic information systems, and on remote data-exchange systems (e.g., the Internet). The progress made so far in the development of the computer system is reviewed. The system has been named the “Relational Accident Database Management System for Mexican Federal Roads” (SAIACF, in Spanish). The information sources beneficial to this project are identified and analyzed. The ideal scheme conceived for the integration of the various information sources is presented, and the SAIACF system is outlined. Some of the results obtained after its application to the information corresponding to 1997 are shown. Also, the element that was generated to make the information and the tools available to users is described, and conclusions are drawn.
Accident Prediction Models With and Without Trend: Application of the Generalized Estimating Equations Procedure
Authors: Lord Dominique , Persaud Bhagwant N.
Published: April 2007

Accident prediction models (APMs) are useful tools for estimating the expected number of accidents on entities such as intersections and road sections. These estimates typically are used in the identification of sites for possible safety treatment and in the evaluation of such treatments. An APM is, in essence, a mathematical equation that expresses the average accident frequency of a site as a function of traffic flow and other site characteristics. The reliability of an APM estimate is enhanced if the APM is based on data for as many years as possible, especially if data for those same years are used in the safety analysis of a site. With many years of data, however, it is necessary to account for the year-to-year variation, or trend, in accident counts because of the influence of factors that change every year. To capture this variation, the count for each year is treated as a separate observation. Unfortunately, the disaggregation of the data in this manner creates a temporal correlation that presents difficulties for traditional model calibration procedures. An application is presented of a generalized estimating equations (GEE) procedure to develop an APM that incorporates trend in accident data. Data for the application pertain to a sample of four-legged signalized intersections in Toronto, Canada, for the years 1990 through 1995. The GEE model incorporating the time trend is shown to be superior to models that do not accommodate trend and/or the temporal correlation in accident data.
Heuristic Vehicle Classification Using Inductive Signatures on Freeways
Authors: Sun Carlos , Ritchie Stephen G.
Published: April 2007

Vehicle classification is the process of separating vehicles according to various predefined classes. Vehicle-classification information can be used in many transportation applications, including road maintenance, emissions/pollution estimation, traffic modeling and simulation, traffic safety, and toll setting. An example of a classification scheme using the following seven vehicle classes is presented: cars, sport-utility vehicles/ pickups, vans, limousines, buses, two-axle trucks, and trucks with more than two axles. This system uses vehicle inductive signatures collected from existing loop-detector infrastructure. It also uses a heuristic-discriminant algorithm for classification and a multi-objective optimization for training the heuristic algorithm. Feature vectors obtained by processing inductive signatures are used as inputs into the classification algorithm. Three different heuristic algorithms were developed, yielding encouraging results of 81 to 91 percent overall classification rates. The results demonstrate the potential of collecting network-wide vehicle-classification data from inductive loops. The availability of vehicle-classification data helps to improve traffic surveillance and better defines dynamic traffic networks.
Conjoint-Based Model of Activity Engagement, Timing, Scheduling, and Stop Pattern Formation
Authors: Wang Donggen , Timmermans Harry
Published: April 2007

Although stated preference or conjoint-based models have recently found ample application in the transportation literature, there have been no attempts to use this modeling approach to develop an activity-based model of transport demand. The development of such a model, called COBRA, is discussed. The model examines individuals’ choices on activity engagement, scheduling, and stop pattern formation. The model is calibrated using experimental design data collected to examine the potential effects of several policies recently proposed in the Netherlands. The modeling results indicate that although people prefer activity schedules involving fewer home-based tours, they do not prefer the combination of all individual trips into a single home-based tour. Furthermore, it is found that individuals will change their activity engagement patterns only if government policies induce substantial changes in individuals’ time availability.
Modeling Learning and Evolutionary Adaptation Processes in Activity Settings: Theory and Numerical Simulations
Authors: Timmermans Harry , Arentze Theo , Joh C. H.
Published: April 2007

The development of a conceptual framework to build a model of multi-faceted choices underlying activity behavior is described. The conceptual framework views individuals developing stereotype behavior or scripts over time by learning. Various principles of learning as a function of state-dependent variables and as a function of latent behavior and adjustment principles are developed and formalized. The focus is on modeling long-term dynamics in activity choice heuristics. Theory, illustrated by a set of numerical experiments, is developed.
Activity-Travel Patterns of Nonworkers in the San Francisco Bay Area: Exploratory Analysis
Authors: Misra Rajul , Bhat Chandra
Published: April 2007

Analysis of activity-travel patterns is an important component of any activity-based transportation planning exercise. Most of the current activity-travel literature focuses on studying the characteristics of workers. In comparison, little emphasis has been placed on studying non-worker activity-travel patterns. The results of an exploratory analysis of the activity-travel patterns of nonworkers in the San Francisco Bay Area are presented. The attributes of a nonworker’s overall activity-travel pattern are examined in terms of three dimensions: number of stops of each activity type, trip chaining, and the temporal sequencing of activities. Implications for transportation planning and policy analysis are discussed.
Determinants of Distance Thresholds for Driving
Authors: Gärling Tommy , Boe Ole , Golledge Reginald G.
Published: April 2007

The hypothesis that habitual drivers become averse to exerting physical effort by walking was tested. In support of the hypothesis, distance thresholds for driving measured in a Swedish ( n = 60) and a U.S. sample ( n = 51) of undergraduates decreased with driving habit. Respondents in the U.S. sample were more frequent drivers and had a lower distance threshold than respondents in the Swedish sample.
Evaluating the Effects of Traveler and Trip Characteristics on Trip Chaining, with Implications for Transportation Demand Management Strategies
Authors: Wallace Brett , Barnes Jennifer , Rutherford G. Scott
Published: April 2007

The relative effect that each of a wide variety of factors has on the extent to which a traveler will chain trips was investigated. The objectives were to empirically determine which factors influence a traveler’s tendency to chain two or more trips within one tour, as well as the relative significance of these considerations; to more specifically determine the level of influence that urban centers have on trip chaining; and to evaluate the potential effects on trip-chaining behavior of specific transportation demand management (TDM) strategies through examination of variables that describe effects associated with TDM. A negative binomial regression model was developed in which the number of trips in a chain is related to household characteristics, traveler characteristics, trip characteristics, and urban form. After the model was estimated, the significance of individual variables was analyzed. Characteristics from each of these categories were found to be statistically significant. A number of the significant variables help to describe effects of specific TDM strategies, and the relative effects of these variables on trip-chaining behavior were addressed. Some of the variables representing TDM strategies increased the level of trip chaining, whereas other variables decreased the level of chaining. Potential policy conflicts between trip chaining and specific TDM programs are discussed.
Assessing Potential for Modal Substitution from Statewide Freight Commodity Flow Data
Authors: Aultman-Hall Lisa , Johnson Bradford , Aldridge Brian
Published: April 2007

Kentucky, despite its relatively small area, has an extensive multimodal freight transportation network. Presented are findings of the statewide freight commodity flow analysis that relate to one of the multimodal transportation planning issues currently facing Kentucky—the relative role of various modes in freight transport and the potential for modal substitution. Issues affecting the type of data required for statewide freight planning studies also are discussed. Statewide issues, such as modal substitution questions, require freight commodity data by origin, destination, and mode. The aggregation of data from the Bureau of Transportation Statistics or other publicly available data was considered unfeasible and the study team was referred to Reebie Associates for detailed freight commodity flow information. The Reebie freight commodity flow data were analyzed by mode, commodity, and spatial zone within Kentucky to determine where the potential for modal substitution was greatest. Three areas of the state were found in which improvements for intermodal facilities for water and rail transportation might be considered. The data confirmed the extent of Kentucky’s multimodal reliance, that is, the majority of freight (by weight and volume) traveling to and from Kentucky moves by nonhighway modes. However, it was also noted that rail and water connections between Kentucky and certain areas of the United States may need further consideration because almost all freight to and from these areas moves by truck. Several other projects within the state are ongoing with these data.
Algorithm for Estimating Mean Traffic Speed with Uncalibrated Cameras
Authors: Dailey Daniel J. , Li Li
Published: April 2007

Presented is a new algorithm for estimating speed by using a sequence of video images from an uncalibrated camera. An assertion is made that exact calibration is not necessary for estimating speed. Instead, the following are used to propose a novel method that extracts scale information and estimates speed: ( a) geometric relationships inherently available in the image; ( b) some common sense assumptions that reduce the problem to a one-dimensional geometry; ( c) frame differencing to isolate moving edges and to track vehicles between frames; and ( d) the distribution of vehicle lengths.
Evaluation of Online Travel Time Estimators and Predictors
Authors: Lindveld Charles D. R. , Thijs Remmelt , Bovy Piet H. L. , Van der Zijpp Nanne J.
Published: April 2007

Travel time is an important characteristic of traffic conditions in a road network. Up-to-date travel time information is important in dynamic traffic management. Presented are the findings of a recently completed research and evaluation program called DACCORD, regarding the evaluation of tools for online estimation and prediction of travel times by using induction loop detector data. Many methods exist with which to estimate and predict travel time by using induction loop data. Several of these methods were implemented and evaluated in three test sites in France, Italy, and the Netherlands. Both cross-tool and cross-site evaluations have been carried out. Travel time estimators based on induction loop detectors were evaluated against observed travel times and were seen to be reasonably accurate (10 percent to 15 percent root mean square error proportional) across different sites for uncongested to lightly congested traffic conditions. The evaluation period varied by site from 4 to 30 days. Results were seen to diverge at higher congestion levels: at one test site, congestion levels were seen to have a strong negative impact on estimation accuracy; at another test site, accuracy was maintained even in congested conditions.
Automobile Patterns of Diffusion in Four Urban Areas: Comparison of Developed and Developing Countries
Authors: Strambi Orlando , Hubert Jean-Paul , Bussière Yves , van de Bilt Karin-Anne
Published: April 2007

A comparison is presented of the diffusion of the automobile in the metropolitan areas of Paris and Montreal and in two urban areas in developing countries—São Paulo, Brazil, and Puebla, Mexico. The comparison uses a demographic approach, based on the estimation of an age-cohort model. The model takes into account three combined aspects of time: the stage in the life cycle, the generation, and the period. Previous analyses conducted for developed countries indicated that the period effect (including the influence of income) could be considered as residual, in the face of stability of behavior of generations during the observed part of their life cycles. Models for the regions were estimated by using a series of transportation surveys (with the exception of Puebla). The results indicate that comparable patterns can be observed with respect to the life cycle and generation effects, although the ages and generations at which maximum motorization occurs vary among countries, according to their different histories of diffusion of the automobile. On the other hand, the spatial pattern of household motorization presents some fundamental differences for the urban areas of developed and developing countries. Paris and Montreal have higher motorization in the suburbs, but the results for São Paulo and Puebla show the opposite, suggesting the relevance of income effects because the populations in suburban areas have lower income levels.
Determining the Number of Probe Vehicles for Freeway Travel Time Estimation by Microscopic Simulation
Authors: Chen Mei , Chien Steven I. J.
Published: April 2007

Using probe vehicles to collect real-time traffic information is considered an efficient method in real-world applications. How to determine the minimum number of probe vehicles required for accurate estimate of link travel time is a question of increasing interest. Although it usually is assumed that link travel time is normally distributed, it is shown, on the basis of simulation results, that sometimes this is not true. A heuristic of determining the minimum number of probe vehicles required is developed to accommodate this situation. In addition, the impact of traffic volume on the required probe vehicle number is discussed.
Archived Intelligent Transportation System Data Quality: Preliminary Analyses of San Antonio TransGuide Data
Authors: Turner Shawn , Albert Luke , Gajewski Byron , Eisele William
Published: April 2007

Described are three data quality attributes that are considered relevant to intelligent transportation system (ITS) data archiving: suspect or erroneous data, missing data, and data accuracy. Preliminary analyses of loop detector data from the TransGuide system in San Antonio were performed to identify the nature and extent of these data quality concerns in typical archived ITS data. The findings of the analyses indicated that missing data were inevitable, accounting for about one in five of all possible data records. Error detection rules were developed to screen for suspect or erroneous data, which accounted for only 1 percent of all possible data records. Baseline testing of TransGuide detector accuracy showed mixed results; one location collected traffic volumes within 5 percent of ground truth, whereas traffic volumes at another location ranged from 12 to 38 percent of ground truth. It was concluded that data quality procedures will be essential for realizing the full potential of archived ITS data.
Intelligent Transportation System Data Archiving: Statistical Techniques for Determining Optimal Aggregation Widths for Inductive Loop Detector Speed Data
Authors: Gajewski Byron J. , Turner Shawn M. , Eisele William L. , Spiegelman Clifford H.
Published: April 2007

Although most traffic management centers collect intelligent transportation system (ITS) traffic monitoring data from local controllers in 20-s to 30-s intervals, the time intervals for archiving data vary considerably from 1 to 5, 15, or even 60 min. Presented are two statistical techniques that can be used to determine optimal aggregation levels for archiving ITS traffic monitoring data: the cross-validated mean square error and the F-statistic algorithm. Both techniques seek to determine the minimal sufficient statistics necessary to capture the full information contained within a traffic parameter distribution. The statistical techniques were applied to 20-s speed data archived by the TransGuide center in San Antonio, Texas. The optimal aggregation levels obtained by using the two algorithms produced reasonable and intuitive results—both techniques calculated optimal aggregation levels of 60 min or more during periods of low traffic variability. Similarly, both techniques calculated optimal aggregation levels of 1 min or less during periods of high traffic variability (e.g., congestion). A distinction is made between conclusions about the statistical techniques and how the techniques can or should be applied to ITS data archiving. Although the statistical techniques described may not be disputed, there is a wide range of possible aggregation solutions based on these statistical techniques. Ultimately, the aggregation solutions may be driven by nonstatistical parameters such as cost (e.g., “How much do we/the market value the data?”), ease of implementation, system requirements, and other constraints.
Traffic Management Parameters from Single Inductive Loop Detectors
Authors: Cherrett Tom , Bell Hugh , McDonald Mike
Published: April 2007

Investigated are potential new uses for the digital output produced by single inductive loop detectors (2 m x 1.5 m and 2 m x 6.5 m) used in most European urban traffic control systems. Over a fixed time period, the average loop-occupancy time per vehicle (ALOTPV) for a detector being sampled every 250 ms is determined by taking the number of 250-ms occupancies and dividing by the number of vehicles. In a similar way, the average headway time between vehicles (AHTBV) is determined by taking the number of 250-ms vacancies and dividing by the number of vehicles. Over a 30-s period, the minimum and maximum values of ALOTPV and AHTBV ranged from 1 to 120 (an ALOTPV of 1 and an AHTBV of 120 representing free-flow conditions, an ALOTPV of 120 and an AHTBV of 1 representing a stationary queue). Identifying periods when a link was operating under capacity and at capacity and when it had become saturated could be more clearly identified by using plots of ALOTPV and AHTBV data over time compared to the more traditional percentage occupancy output. ALOTPV also was used to successfully identify long vehicles from cars down to speeds of 15 km/h.
Using Weigh-in-Motion Data to Calibrate Trade-Derived Estimates of Mexican Trade Truck Volumes in Texas
Authors: Figliozzi Miguel A. , Harrison Robert , McCray John P.
Published: April 2007

Weigh-in-motion (WIM) sites are being installed along many highway corridors that carry international trade trucks. Estimating the numbers of trucks carrying international commodities currently relies on manipulating and adjusting trade databases. The variety of vehicle classification data measured at WIM sites provides a rich source of data with which to enhance this adjustment process. Previous WIM border data have focused on port-of-entry truck traffic axle loads, which are heavily influenced by drayage operations. Examined is how WIM data collected at ports of entry and on truck corridors can be used in the determination of standardized truck volumes (termed equivalent trade trucks or ETT) on international highway corridors. Data from the Texas-Mexico border are used to determine ETT North American Free Trade Agreement volumes.
Use of Respondent-Interactive Geocoding in Baltimore, Maryland, Mode Choice Survey
Authors: Adler Thomas , Rimmer Leslie , Bandy Gene , Schellinger David
Published: April 2007

Most travel surveys collect information about the locations of trip origins and destinations. The process of translating the location data collected in surveys into information that can be used in transportation planning, called geocoding, historically has been difficult and error prone. Geographic information system data and tools increasingly have been used to improve the process. Described is a new approach to geocoding that was developed and used in a recent mode choice survey conducted for the Baltimore (Maryland) Metropolitan Council. This approach, in which respondents complete the geocoding process themselves, is designed for use in a computer-assisted self-interview survey. Respondents are given tools that allow them to specify a street address, a nearest intersection, a business name, or a map location to locate the place that they visited. In the Baltimore application, respondents actively used all four methods. The analysis of how the methods were used indicates that the geocoding process benefits from providing all four of these options to respondents.
Improving Survivability of Intelligent Transportation Systems: Application-Level Intrusion Detection Case Study
Authors: Smith Brian L. , Sielken Robert S.
Published: April 2007

Intelligent transportation systems (ITS) are deployed around the world to improve the safety and efficiency of surface transportation through the application of advanced information technology. However, ITS expose the transportation system to new vulnerabilities, making it imperative that those implementing such systems design them to be more survivable. The approaches most commonly used to increase the survivability of ITS are physical security, hardware redundancy, and software and data backups. An essential element of a survivable system that has not been adequately addressed is intrusion detection. Intrusion detection seeks to identify individuals who have gained unauthorized access to a system, as well as those with authorized access who are abusing the system. Described is the importance of robust intrusion detection for ITS (and other transportation information systems). The state of the practice in intrusion detection is summarized, and a case study is presented that investigates the development of an intrusion detection system (IDS) conceptual design for an essential element of ITS, electronic toll collection. Through the case study, the researchers found that intrusion detection at the application level could significantly improve the overall surviv-ability of ITS. From this finding, it is clear that there is a need to commit resources to developing application level IDS for the wide range of ITS. Given the importance of surface transportation to a region’s economy and the potential vulnerabilities introduced by ITS, it is imperative that further work be conducted to increase the survivability of ITS.
Asset Management Model and Systems Integration Approach
Authors: Tao Zongwei , Zophy F. Gordon , Wiegmann John
Published: April 2007

Transportation asset management is an integrated set of best practices and systems that achieve optimal and cost-effective investment and use of transportation assets throughout their service life cycle. Most infrastructure management programs and systems contain certain elements of asset management functions. However, they lack a strong capacity to accomplish the overall asset management goal. Presented is an asset management model together with an approach for systems integration. The asset management model illustrates basic asset management goals, strategies, principles, and analysis methods. An example of an integrated maintenance program incorporates the features of the model. Supporting the asset management model is a systems integration approach that demonstrates how component asset management systems can be integrated at different stages of their development life cycles. The integration process is needed to ensure that system interoperability truly supports an effective asset management program. The approach can be defined in five phases: ( a) business integration, ( b) system requirements integration, ( c) logical design integration, ( d) physical design and development integration, and ( e) implementation integration. Each phase carries a particular integration objective and develops unique integration products. An operational scenario tool is introduced as an implementation strategy for asset management.
Geographic Information System Procedures to Improve Speed and Accuracy in Locating Crashes
Authors: Elise Carreker Lauren , Bachman William
Published: April 2007

Locating statewide crashes for system or facility analyses can be difficult and time-consuming. In many localities, crash data are manually transcribed from paper crash reports and then located, by a separate operator, on a linear reference scheme. Data quality and quantity reduce an operator’s ability to accurately identify route and milepoint locations for a large percentage of crashes. A study of crash data in Georgia has identified potential location errors. The study also revealed that numerous technical solutions such as improved data transcription guidelines, multiple public and private road databases, geographic information systems, and standard relational databases potentially can strengthen the functionality of crash location systems. An analysis of an existing crash location procedure is described, and alternatives techniques designed to speed the location process and improve location accuracy are discussed.
Cost-Benefit Analysis of Geographic Information System Implementation: Illinois Department of Transportation
Authors: Hall James P. , John Kim Tschangho , Darter Michael I.
Published: April 2007

An in-depth investigation of the costs and benefits of geographic information system (GIS) implementation in the Illinois Department of Transportation (IDOT) is presented. The investigation addresses a critical need to determine the organizational impact and cost-effectiveness of this enter-prisewide information technology to achieve the greatest benefit. IDOT conducted an enterprise wide effort to portray GIS capabilities and to identify candidate GIS projects. Fourteen major GIS projects were selected on the basis of management priority, ease of implementation, and user commitment. A comprehensive cost-benefit analysis was developed over fiscal years 1995 through 2004. Costs were reasonably estimated from historical costs of the GIS investigation effort and future costs of GIS technical support and user area resources. The greatest portions of costs, over the 10-year time frame, were for personnel (67 percent) and consultant services (19 percent). For the more difficult benefits determination, the research employed two categories of benefits: efficiency and effectiveness. Efficiency benefits would result from the automation of previous manual efforts, such as special-purpose cartographic production, with GIS outputs. Effectiveness benefits arise from traditionally intangible areas, such as increased integration and accessibility of information for improved decision making. Effectiveness benefits were estimated conservatively for two high-priority areas: accident analysis and program development. The result of the cost-benefit analysis of GIS implementation yielded a net present value of $2.9 million and an internal rate of return of 99.8 percent over the analysis period. This provided IDOT management with knowledge for strategic resource allocation decisions.
Evaluation of Portable Concrete Barriers Using Finite Element Simulation
Authors: Marzougui Dhafer , Bahouth George , Eskandarian Azim , Meczkowski Leonard , Taylor Harry
Published: April 2007

The use of finite element (FE) simulations in modeling and evaluating roadside hardware has increased significantly in the past few years. Thanks to the remarkable improvements in computer technology and finite element software, the crash behavior of automobiles and roadside hardware objects can be predicted. Finite element simulations were used to evaluate the safety of portable concrete barriers (PCB). The first step was to develop a methodology for creating accurate FE representations of PCBs. This objective was achieved by developing an FE model of an F-shape PCB design and using full-scale crash test data to validate the model. Once the fidelity and accuracy of the modeling methodology had been proved, FE models of two modified PCB designs were created and their safety performance was evaluated. Based on the simulation results, a third design was developed and its performance was analyzed. The safety performance of the three designs was compared.
Impact Performance of the G4(1W) and G4(2W) Guardrail Systems: Comparison Under NCHRP Report 350 Test 3-11 Conditions
Authors: Plaxico Chuck A. , Ray Malcolm H. , Hiranmayee Kamarajugadda
Published: April 2007

Several types of strong-post W-beam guardrails are used in the United States. Usually the only difference between one type of strong-post W-beam guardrail and another is the choice of post and block-out types. The impact performance of two very similar strong-post W-beam guardrails are compared—the G4(2W), which uses a 150×200 mm wood post and the G4(1W), which uses a 200×200 mm wood post. Although G4(2W) is used in numerous states, G4(1W) is now common only in the state of Iowa. The performance of the two guardrails has been presumed equal, but only one full-scale crash test has been performed on G4(1W) and that was over 30 years ago, using a now-obsolete test vehicle. The nonlinear finite element analysis program LS-DYNA was used to evaluate the crashworthiness of the two guardrails. The G4(2W) guardrail model was validated with the results of a full-scale crash test. A model of the G4(1W) guardrail system was developed, and the deflection, vehicle redirection, and occupant risk factors of the two guardrails were compared. The impact performance of the two guardrails was quantitatively compared using standard techniques. The analysis results indicate similar collision performance for G4(1W) and G4(2W) and show that both satisfy NCHRP Report 350 Test 3-11 safety performance requirements.
Performance of Breakaway Cable and Modified Eccentric Loader Terminals in Iowa and North Carolina: In-Service Evaluation
Authors: Ray Malcolm H. , Hopp Jeffery A.
Published: April 2007

Developing safe and effective guardrail terminals has been a high priority for roadside safety researchers for several decades. Numerous full-scale crash tests have been performed, and many new types of terminals have been developed. Results are presented of an in-service performance evaluation of two popular guardrail terminals—the breakaway cable terminal and the modified eccentric loader terminal. The data were collected in parts of Iowa and North Carolina during a 24-month period from 1997 to 1999. The collision characteristics, occupant injuries, and barrier damage were evaluated to determine collision performance.
Design and Development of Steel Breakaway Posts
Authors: Sicking Dean L. , Rohde John R. , Reid John D.
Published: April 2007

The current generation of NCHRP Report 350-compliant guardrail terminals all use wooden breakaway posts in the terminal section. The first two end posts are typically breakaway cable terminal posts inserted into steel foundation tubes that are joined with a ground strut to provide the anchorage capacity. Wood is readily available and inexpensive, but it also has many drawbacks. The quality of the wood and the associated breaking forces vary widely. The strength of a wooden post is affected by many factors, including post size, ring density, knot location and size, cracks and checks, species, and moisture content. Results are presented of an effort to design and develop steel breakaway posts for guardrail terminals. The breakaway steel post system described has been successfully tested for use in a tangent terminal. The post exhibited consistent strength for redirection impacts and failed at very low loads during head-on impacts. The breakaway steel post actually improved the redirective performance of the SKT-350 during a 2020-kg (4,450-lb) pickup truck impact at the beginning of the length of need. These breakaway steel posts have been shown to meet NCHRP Report 350 performance criteria and should provide highway agencies with an alternative where wood posts are unacceptable.
Evaluating Human Risk in Side Impact Collisions with Roadside Objects
Authors: Ray Malcolm H. , Hiranmayee Kamarajuggada
Published: April 2007

Full-scale crash tests are traditionally used to assess the danger posed by roadside object. Crash test evaluation criteria should relate the observable response of the vehicle and the struck object to the likely risk of injury to vehicle occupants in similar real-world collisions. Side impact collisions are particularly serious impacts, but no evaluation guidelines exist. A simple method is presented for determining human risk in a side impact collision with a roadside object from the velocity profile of the impacted face of the struck object. This method not only eliminates the use of anthropometric test devices in crash tests, but also gives conservative values to account for the variable occupant position at the time of impact.
In-Service, Performance-Based Roadside Design Policy: Preliminary Insights from Washington State’s Bridge Rail Study
Authors: Shankar Venkataraman N. , Albin Richard B. , Milton John C. , Nebergall Marylou
Published: April 2007

Empirical insights about the performance of in-service roadside hardware are presented. A statistical study of bridge rail impacts on vehicular accident severity is presented from data collected in Washington State. In particular, concrete balusters and metal rails underperformed in comparison with the average bridge rail type, whereas thrie-beam guardrails and safety shape barriers had superior performance. The study presents a statistical framework that is particularly suitable for capturing real-world, unobserved effects that impact reported accident severity distribution. Policy sensitivities show systemwide savings through upgrading the underperforming rails to provide substantial performance. The combination of insights from the relative performance of bridge rails and the associated policy sensitivities provides direction for national policy on roadside design. In particular, the insights offer some strategic direction on inexpensive upgrades to state-level decision making.
Test Level 4 Bridge Rails
Authors: Eugene Buth C. , Menges Wanda L. , Williams William F.
Published: April 2007

Design details and full-scale crash test results are presented for three bridge rails tested for compliance with NCHRP Report 350 Test Level 4 requirements. Designs of these rails are based on AASHTO LRFD Bridge Design Specifications. Each bridge rail consists of structural steel tubing rail elements mounted on wide-flange posts. The rails are generally stronger than many designs commonly used in the recent past. Full-scale crash test results demonstrated that all bridge rails meet NCHRP Report 350 safety performance requirements.
Estimation of Time of Concentration for Maryland Streams
Authors: Thomas Wilbert O. , Monde Michele C. , Davis Stanley R.
Published: April 2007

The time of concentration (TC) is an important input to most hydrologic models and is usually estimated by travel-time computations or by using rainfall-runoff data. Average TCs were determined for 78 rural and urban watersheds in Maryland and related to watershed characteristics using regression analysis. The regression equation is based on the channel length and slope; the percentage of the watershed covered with forests, lakes, and ponds; and the percentage of the watershed with impervious areas. The equation is applicable for estimating TCs for rural and urban watersheds in Maryland with watershed characteristics similar to the gauging station data. TC values computed at Maryland gauging stations were compared with estimates from an equation developed by Kirpich and the Soil Conservation Service (SCS) lag equation, and with basin lag times determined by the U.S. Geological Survey (USGS). The average TC values computed in this analysis were about 5 percent higher than the basin lag-time estimates, which is consistent with the USGS’s definition of lag time. TC estimates from the Kirpich or SCS equations were consistently lower than the values computed from gauging station data. The tendency to underestimate TCs is a major reason why hydrologic models often provide conservative estimates of design discharges compared with regional regression equations and gauging station data.
Temporal Variations in Heavy Metal Partitioning and Loading in Urban Highway Pavement Sheet Flow: Implications for In Situ Treatment Design
Authors: Sansalone John J. , Glenn Donald W.
Published: April 2007

In situ treatment design for pavement storm water runoff continues to pose unique challenges because of the unsteady nature of processes such as rainfall runoff, mobilization, partitioning, and delivery of heavy metals. Storm water from pavements and roadways transports dissolved, colloidal, and suspended solids in a heterogeneous mixture, and along with pH, alkalinity, traffic levels, and residence time, influences the partitioning of heavy metals. For effective in situ treatment design, an understanding of heavy metal partitioning and temporal wash-off during a rainfall runoff event is a prerequisite. This study investigates zinc (Zn), cadmium (Cd), copper (Cu), and lead (Pb) partitioning, cumulative loadings, and wash-off in storm water pavement sheet flow from a heavily traveled urban interstate pavement site. Results are presented for a series of eight rainfall runoff events at the instrumented site. Results from partitioning analysis (heavy metal mass transfer) between the dissolved and particulate-bound fractions indicate that Zn, Cd, and Cu masses are predominately dissolved in pavement sheet flow, qsf. Although a relatively insoluble heavy metal, Pb mass was also mostly dissolved. These high dissolved fractions can be attributed to low urban rainfall pH levels, relatively short pavement residence times for the qsf, and low pavement runoff alkalinity. Plots of cumulative heavy metal mass as a function of elapsed runoff time clearly demonstrate that during all events the qsf dissolved fractions dominated the particulate fractions for Zn, Cd, Cu, and Pb. As far as delivery, results also indicate that the dissolved masses for Zn, Cd, Cu, and Pb generally exhibited a “first flush” compared with their particulate masses. The design of in situ treatment systems or source control best management practices loaded by qsf require data on partitioning and loading for effective treatment.
California Department of Transportation Statewide Storm Water Management Program
Authors: Johnston John , Yamaguchi Howard , Frankel Andrew
Published: April 2007

The California Department of Transportation (Caltrans) has initiated a comprehensive storm water management program to comply with the requirements of the federal Clean Water Act. The program’s main components include a statewide storm water management plan, monitoring and research studies, and institutional changes. The monitoring and research studies are designed to characterize Caltrans storm water runoff, evaluate the effectiveness of best management practices, and support watershed planning. The institutional changes include training, manuals, standard contract language, and compliance reviews. The program is designed to develop and implement science-based, cost-effective solutions for mitigating the harmful environmental effects of storm water runoff from roadways and related facilities.
Laboratory Performance Evaluation of Cement-Stabilized Soil Base Mixtures
Authors: Mohammad Louay N. , Raghavandra Amar , Huang Baoshan
Published: April 2007

In-place cement-stabilized soils have served as the primary base material for the majority of noninterstate flexible pavements in Louisiana for many years. These materials are economically and easily constructed and provide outstanding structural characteristics for flexible pavements. However, these cement-treated materials crack due to shrinkage, with the cracks reflecting from the base to the surface. A laboratory study examined the performance of four different cement-stabilized soil mixtures recently used in the construction of test lanes at the Louisiana Pavement Testing Facilities. Laboratory tests included the indirect tensile strength and strain, unconfined compressive strength, and indirect tensile resilient modulus tests. The four mixtures were ( a) in-place-mixed cement-treated soil with 10 percent cement, ( b) plant-mixed cement-treated soil with 10 percent cement, ( c) plant-mixed cement-treated soil with 4 percent cement, and ( d) plant-mixed cement-treated soil with 4 percent cement and fiber reinforcement. The results indicated that there was no significant difference in performance between the plant-mixed and in-place-mixed cement-treated soil mixtures. The inclusion of fiber to the cement-treated soil mixture significantly increased the indirect tensile strain and the toughness index. Increases in compaction effort maintained or significantly increased the indirect tensile strength and unconfined compressive strength. Increases in curing period maintained or significantly increased indirect tensile and unconfined compressive strength as well as the resilient modulus of the mixtures.
New Method to Stabilize the Uplift-Pressure Problem for Raft Foundations
Authors: Ta-Teh Chang Dave , Chang Jeffery C.I. , Tung Roger S.T. , Hou H.C.
Published: April 2007

In Taipei City, the deep-raft foundation is the most common foundation type for typical commercial buildings. It is known that deep-raft foundations below a high groundwater table are associated with uplift-pressure problems. Conventional solutions, such as increased dead weight, tension piles, or ground anchors, are costly, time consuming, and sometimes inefficient. A successful approach using a geosynthetic system to stabilize and relieve the hydrostatic uplift pressure within the impervious strata is presented. Filtration, clogging, transmissivity, and other properties of geosynthetics are specified to assure the dissipation of uplift pressure in the long run. The design concept was applied in practice to a multistory commercial complex. Two typical cases are introduced. Monitoring results are also covered. Based on the site experience, the installation of this system was found to be rapid, simple, and cost-effective.
SuperJet Grouting: New Technology for In Situ Soil Improvement
Authors: Burke George K. , Cacoilo David M. , Chadwick Kenneth R.x
Published: April 2007

The New Jersey Department of Transportation solicited a request for proposal for a design-construct bid to extend the Atlantic City Expressway to the marina district and Brigantine. This would service a developing area for casino construction as well as greatly improve access to the beachfront towns north of Atlantic City. The preliminary proposal required approximately 0.8 km (0.5 mi) of four-lane roadway to go underground, eliminating traffic noise, and to pass under US-30. The prime and specialist contractors, in concert with intuitive engineering support, developed an in situ installation of a subgrade bottom-strut bracing system for a cut-and-cover tunnel installation. This concept offered many advantages, including months of schedule savings, reduced sheet-pile cost, and much-reduced wall-anchoring requirements. To economically install this bottom strut, the new system of SuperJet grouting was used. This grouting system offers several key advancements over conventional jet grouting and allows the construction of columns up to 5 m (16 ft) in diameter. This new technology, the method of installation, difficulties overcome, and the quality-assurance and quality-control elements of this portion of the project are presented. Future applications are also proposed.
Determination of Volume of Aggregates: New Image-Analysis Approach
Authors: Rao Chetana , Tutumluer Erol
Published: April 2007

The importance of using quality aggregates with specific gradation and shape properties in asphalt concrete has been recognized by the Strategic Highway Research Program under a set of developed consensus aggregate properties. The flat and elongated ratio and angularity of the aggregate particles are those properties that directly influence the rutting potential of an asphalt pavement. Along with a need to develop rapid and automated methods for determining flat and elongated ratios of individual aggregate particles, there is also a need to develop an accurate and repeatable experimental technique. A new aggregate image analyzer has been recently developed at the University of Illinois that uses three video cameras for accurately determining the volume of each aggregate and for automating the determination of flat and elongated particles, angularity, and gradation. A new image-analysis approach determines the percentage by weight of the flat and elongated particles providing results comparable to the manual results from ASTM D4791 by presenting the results as ratios of weights. The significance of making such accurate volume computations of an individual aggregate using images is discussed. The computed aggregate volumes and the percentages by weight of flat and elongated ratios obtained for two bag samples were in very good agreement with the manual measurements, thus validating the correctness of the imaging technique and the effectiveness of the new aggregate image analyzer.
Measuring Bulk-Specific Gravity of Fine Aggregates: Development of New Test Method
Authors: Kandhal Prithvi S. , Mallick Rajib B. , Huner Mike
Published: April 2007

Bulk specific gravity of the fine aggregate is used in hot-mix asphalt volumetric-mix design (including Superpave) to determine the amount of asphalt binder absorbed by the aggregate and the percentage of voids in the mineral aggregate. The current test method (AASHTO T84) uses a cone method to establish the saturated surface dry (SSD) condition of the sample, which is necessary to conduct the test. This method does not work satisfactorily for fine aggregates that are very angular and have rough surface texture and, therefore, do not slump readily when in SSD condition. A research project was undertaken to develop automated equipment and a method of establishing the SSD condition of the fine aggregate. The wet sample of the fine aggregate is placed in a rotating drum and subjected to a steady flow of warm air. The temperature gradient of the incoming and outgoing air and the relative humidity of the outgoing air are monitored to establish the SSD condition. Two prototype devices were constructed. The test results obtained with the second prototype device are encouraging and are reported. Further improvements to be made to the second prototype device to improve the repeatability and reproducibility of the test have been identified.