bluuebunny/crossref_metadata_2025 huggingface dataset:
Life-Cycle Cost Analysis of Mitigating Reflective Cracking
Authors: Tighe Susan , Haas Ralph , Ponniah Joseph
Published: April 2007

Reflective cracking is a major and costly problem in many countries. It occurs in the top (overlay) layers above existing cracks in the lower (existing) pavement. This type of cracking can lead to premature deterioration of the pavement structure through the infiltration of moisture and debris. Although extensive research has been directed toward mitigation of the problem, work needs to be done, as it still appears to be a major problem. The problem is related in part to the fact that most of the work being done involves rehabilitation. One of the most common types of pavement rehabilitation is the use of an asphalt overlay. The focus of the present analysis is the economic benefits of reducing and treating reflective cracking before the placement of an asphalt overlay. A methodology for converting crack spacing to roughness is also presented. This information is used to examine how cracking is related to the measured international roughness index values. A model relating the amount of cracking to the loss of serviceability or a reduction in service life is presented. That model indicates that a reduction of transverse crack spacing from 5 to 20 m should result in a 5-year extension of service life, with a cost savings of $25,000 (2002 U.S. dollars) per two-lane kilometer. Measurement and treatment of cracking can also yield significant benefits. Benefit–cost ratios from the measurement of cracking can range from about 5 to 50, while proper and timely crack treatment (routing and sealing) can result in an extension of pavement life by 2 years and cost savings of $7,000 per lane kilometer.
Quantitative Field Evaluation and Effectiveness of Fine Mix Under Hot-Mix Asphalt Base in Flexible Pavements
Authors: Al-Qadi Imad L. , Loulizi Amara , Lahouar Samer , Flintsch Gerardo W. , Freeman Thomas E.
Published: April 2007

Testing was conducted with the main objective of predicting the effect of incorporating a fine hot-mix asphalt (HMA) layer under an HMA base on the long-term fatigue performance of flexible pavements. Testing at the Virginia Smart Road allowed the determination of the vertical compressive stress and horizontal transverse strain induced by a steering-axle tire of 25.8 kN (5,800 lb) under the HMA layer of two pavement designs, one of which included a fine surface mix below a base mix. Stresses and strains were measured for four different speeds [8, 24, 40, and 72 km/h (5, 15, 25, and 45 mph)], for three tire inflation pressures [552, 655, and 724 kPa (80, 95, and 105 psi)], and at different temperatures. Stresses were measured with pressure cells, while strains were measured with H-type strain gauges embedded in the HMA layers during construction. As expected, temperature was found to significantly affect the vertical compressive stresses and horizontal transverse strains measured under the HMA layer. Speed, on the other hand, did not affect the magnitude of the vertical compressive stress measured in any of the layers but did affect the loading time. However, speed was found to significantly affect the horizontal transverse strain measured under the HMA layer. The compressive stress and horizontal transverse strain measured at the bottom of the HMA layer at depths greater than 150 mm (6 in.) were found to be independent of tire inflation pressure ranges from 552 to 724 kPa (80 to 105 psi). It appears that incorporation of a fine HMA at the bottom of a HMA base layer would increase the fatigue lives of flexible pavements.
Deployment of Smart Work Zone Technology in Arkansas
Authors: Tudor Lorie H. , Meadors Alan , Plant Robert
Published: April 2007

The Arkansas State Highway and Transportation Department began an extensive pavement rehabilitation program in the spring of 2000 that ultimately will rebuild approximately 380 mi, or 60%, of Arkansas’ total Interstate miles. To improve safety and manage congestion in work zones, the department has deployed smart work zone technology systems on five projects. The main goal for this endeavor was to provide a queue-detection system that will prevent or reduce rear-end collisions and will also provide motorists with real-time information about potential backups caused by lane closures. After each system was installed, a general evaluation of the basic design was conducted. Knowledge gained was applied to each subsequent system, to improve the design and to provide increased effectiveness, reliability, and practicality. The design evolution of these systems is presented, the design development is discussed in detail, and the effectiveness of two of the automated work zone information systems installed on Interstate rehabilitation projects in Arkansas is evaluated. The systems used were ADAPTIR from Scientex Corporation and CHIPS from ASTI Transportation Systems. These systems included all hardware, software, and other equipment necessary for collecting, displaying, and processing traffic condition data. These data were used to provide motorists with real-time speed-control, delay, and diversion advisory messages via portable changeable message signs and a highway advisory radio system.
Guidelines for Application of Portable Work Zone Intelligent Transportation Systems
Authors: Fontaine Michael D.
Published: April 2007

Work zone intelligent transportation systems (WZITSs) are promoted as a way to improve safety and reduce congestion at work zone locations where traditional traffic management centers do not exist. These systems usually integrate portable changeable message signs and speed sensors with a central control system that automatically determines appropriate messages that are based on current traffic conditions. Manufacturers of these systems claim that WZITSs can warn drivers of downstream congestion, alert drivers to slower speeds ahead, and suggest alternate routes on the basis of prevailing conditions. Transportation agencies are often asked to make decisions on the installation of a WZITS without the benefit of objective information on its expected performance. Relatively few operational tests of these systems have been performed, and the results are not always well documented or conclusive. Agencies need guidance to help them determine whether a WZITS system would improve safety and operations at a specific site. Applications of WZITSs are reviewed, and a series of guidelines for their deployment, based on lessons learned from past tests, is presented.
Computerized Equipment Replacement Methodology
Authors: Weissmann José , Jannini Weissmann Angela , Gona Srinivas
Published: April 2007

The Texas Department of Transportation (DOT) owns and maintains an active fleet inventory of approximately 17,000 units and replaces about 10% of them annually. Any methodology that can improve Texas DOT’s replacement procedures could potentially save millions of dollars. Private and public agencies do not routinely use life-cycle cost as a replacement criterion because the only way to automate inspection of thousands of life-cycle cost histories has been to define an acceptability threshold for annualized costs. Most fleet managers consider this practice too inaccurate. The most relevant information provided by a lifecycle cost graph is its trend. Units whose life-cycle costs have been increasing longer or at a faster rate should have higher replacement priority. The trend score concept allows a computer to mimic replacement decisions made by a person visually inspecting a series of life-cycle cost histories. A new economically sound methodology for assisting with equipment replacement at Texas DOT is presented. This new method takes full advantage of Texas DOT’s comprehensive equipment operating system database, can prioritize the units on the basis of comparisons among all units within any desired class of equipment, and uses life-cycle cost trends as a replacement criterion. This methodology was implemented through the Texas Equipment Replacement Model, a menudriven software that allows the fleet manager to efficiently apply the methodology.
Pricing Commuter, Intercity, and Freight Trains in a Terminal Railway Context: An Approach
Authors: Bertie Bryan K.
Published: April 2007

The cost-of-service (or fully allocated cost) pricing model has been criticized in the economics literature. The criticisms generally focus on the issues of cross-subsidization problems from using average costs and economically inefficient pricing. A fully allocated cost model, applied to a terminal railroad setting, is presented that can substantively overcome these criticisms by using a resource consumption approach for key cost drivers. A successful implementation of a new cost recovery system in Toronto, Ontario, Canada, is used that applies these resource consumption concepts. A necessary precondition to this approach is the charting of the classes of traffic (commuter, intercity, and freight) into operated-track segmented paths, each of which consists of a set of one or more track links. Each traffic class path is characterized as either consisting of sole-use links, joint-use links, or a combination thereof. Operating and capital costs directly attributable to the track links are calculated. A reverse engineering work-effort-per-activity approach is used for assigning the total routine maintenance of way and maintenance of signals budget dollars to the terminal track links. The resource consumption approach provides a logical framework and analytical platform for analyzing link infrastructure complexity; system, path, and link capacity; path and link cost performance; and path and link renewal and replacement capital planning and capital sharing responsibility.
Railroad Derailment Factors Affecting Hazardous Materials Transportation Risk
Authors: Barkan Christopher P. L. , Dick C. Tyler , Anderson Robert
Published: April 2007

U.S. freight railroad accident and hazardous materials release rates have declined substantially since 1980. Ironically, this trend has made the identification and implementation of further safety improvement options more challenging because less empirical information exists on which accident causes present the greatest risks. Consequently, more sophisticated methods are needed to identify the best options for transportation risk reduction. Of particular interest is identifying the principal causes of accidents that can result in a tank car release of hazardous materials, which can harm people, property, and the environment. Because large hazardous materials release accidents are relatively rare, railroads cannot effectively manage safety improvement efforts solely in response to the causes of specific accidents. Instead, a risk-based approach is needed to better understand predictive factors for conditions that can cause a release. Railroad derailment data were analyzed to identify the conditions most likely to lead to a release accident. The objective was to identify proxy variables that can be used as performance measures. The speed of derailment and number of derailed cars highly correlated with hazardous materials releases. Some accident causes are much more likely to lead to release conditions than others. Accident prevention efforts to reduce these causes are more likely to reduce the risk of major railroad hazardous materials release accidents.
Pavement Management Perspective on Integrating Preventive Maintenance into a Pavement Management System
Authors: Zimmerman Kathryn A. , Peshkin David G.
Published: April 2007

Many transportation agencies use pavement preservation programs to manage their pavement assets cost-effectively. One important aspect of pavement preservation is the use of preventive maintenance treatments to improve the functional condition of the network and retard the overall rate of deterioration. Because preventive maintenance treatments are less expensive than resurfacing or reconstruction projects, a preventive maintenance program can provide a cost-effective means of meeting pavement performance goals. Pavement management systems support pavement preservation strategies in important ways. They assist in identifying and prioritizing preventive maintenance needs, justifying funding levels, and evaluating the long-term impacts of various preservation strategies. To date, many agencies have operated preventive maintenance activities in isolation from pavement management programs. However, many potential benefits can be gained from the closer integration of these two activities. A transportation agency that wishes to integrate preventive maintenance and pavement management might be required to make several changes. Specific technical areas in which changes might be needed include condition surveys and condition index calculations, pavement performance models, treatment rules, and program development. In addition, several institutional issues must be addressed to successfully integrate the two programs. Examples from state highway agencies illustrate possible solutions.
Development of Structural Condition Index to Support Pavement Maintenance and Rehabilitation Decisions at Network Level
Authors: Zhang Zhanmin , Claros German , Manuel Lance , Damnjanovic Ivan
Published: April 2007

Every year, state highway agencies apply large amounts of seal coats and thin overlays to pavements to improve the surface condition, but these measures do not successfully address the problem. Overall pavement condition continues to deteriorate because of the structural deformation of pavement layers and the subgrade. To make effective decisions about the type of treatment needed, one should take into consideration the structural condition of a pavement. Several different structural estimators can be calculated by using falling weight deflectometer data and information stored in the Pavement Management Information System (PMIS) at the Texas Department of Transportation. The analysis considers pavement modulus and structural number as the structural estimators of a pavement. The evaluation method is based on the sensitivity of the structural estimators to deterioration descriptors. The deterioration per equivalent single-axle load of all major scores stored in the Texas PMIS is proposed as the primary indicator of pavement deterioration. In addition, the use of the structural condition index is recommended as a screening tool to discriminate between pavements that need structural reinforcement and those that do not. This index is calibrated for use in maintenance and rehabilitation analysis at the network level.
Implementation of Virtual Reality in Routine Bridge Inspection
Authors: Jáuregui David V. , White Kenneth R.
Published: April 2007

The innovative use of QuickTime Virtual Reality (QTVR) and panoramic image–creation utilities for recording field observations and measurements during routine bridge inspections is reported. A virtual reality approach provides the ability to document a bridge’s physical condition by using different media types at a significantly higher level of detail than is possible in a written bridge inspection report. Digitally recorded data can be stored on compact disc for easy access before, during, or after an inspection. The development of a QTVR bridge record consists of four major steps: selection of the camera stations, acquisition of the digital images, creation of cylindrical or cubic panoramas, and rendering of the QTVR file. Specific details related to these steps are provided, as applied to various bridge inspection projects. The potential impact of QTVR on bridge management—in which routine inspection data are a factor in making decisions regarding the future maintenance, rehabilitation, or replacement of a bridge—is discussed.
Adhesive Applications Used During Repair and Strengthening of 30-Year-Old Prestressed Concrete Girders
Authors: Reed Calvin E. , Peterman Robert J. , Rasheed Hayder , Meggers David
Published: April 2007

The use of polymer adhesives during the strengthening of 30-year-old prestressed concrete bridge girders is described. The single-T–shaped specimens strengthened in this study were saw-cut from prestressed concrete double-T girders that had been removed from a bridge originally designed for H-15 highway loading and opened to traffic in 1969. Over time, the bridge had been severely overloaded, resulting in numerous flexural and shear cracks in the stems of each girder and large concrete spalls at the tension faces. In 1998, several damaged members were replaced. To investigate the feasibility of repairing or strengthening similar members in the future, the damaged members were retrofitted with carbon fiber–reinforced polymer (CFRP) sheets and then load tested under service and ultimate load conditions. Polymer adhesives were used to seal all visible cracks in the stems, to inject epoxy into all sealed cracks, to fill spalled areas in the tension face of the stems, to apply longitudinal and transverse CFRP sheets to the stems of the members, and to install near-surface-mounted reinforcement (NSMR) in one of the specimens. Results from load tests indicate that excellent bond was consistently achieved between the CFRP sheets and the 30-year-old concrete surface and between the NSMR and surrounding concrete. The success of epoxy injection of the flexural cracks, however, varied. Specifically, the injected cracks in one specimen reopened at an applied load well below the theoretical cracking load for the members.
Highway Vulnerability Assessment: A Guide for State Departments of Transportation
Authors: Rowshan Shahed , Smith Michael C. , Krill Stephen J. , Seplow Jennifer E. , Sauntry William C.
Published: April 2007

A methodology is provided for state departments of transportation (DOTs) to conduct vulnerability assessments of their highway assets. This tool allows state DOTs to assess the vulnerability of their physical assets, such as bridges and tunnels; to develop possible countermeasures to deter, detect, and delay the consequences of terrorist threats; to estimate the capital and operating costs of such countermeasures; and to improve security operational planning. The audience for this methodology is broad—from senior officials involved in the initial planning stage of the process, to midlevel managers charged with developing the assessment plans and procedures, to field personnel. The state DOTs must organize and manage a multidisciplinary team whose members have a working knowledge of the department’s mission, its critical assets, and its policies, plans, and procedures. The methodology involves six steps for conducting a vulnerability assessment of highway transportation assets. They provide a straightforward method for examining critical assets and identifying cost-effective countermeasures to guard against terrorism. The criteria used in selecting the preferred approaches include availability, accessibility, transparency, replicability, reasonableness, scalability, robustness, costeffectiveness, and modularity.
Airblast Environment Beneath a Bridge Overpass
Authors: Ray James C. , Armstrong Byron J. , Slawson Thomas R.
Published: April 2007

As engineers move into the somewhat new field of assessing vulnerability to terrorist threats, they need to understand the tools available to them and the associated limitations. To facilitate this understanding, an overview of the basic categories of prediction methods for airblast loadings from bomb detonations is presented. The complex problem of bomb detonation beneath an overpass bridge—an area that is semi-enclosed and where numerous reflecting surfaces exist—is used to aid the discussion and to highlight the importance of using the appropriate prediction methods and tools to address problems. Results from three prediction methods are compared. The high-fidelity Second-Order Hydrodynamic Automatic Mesh Refinement Code appears to be superior to the Conventional Weapon Effects Predictions and BlastX codes in terms of accuracy for use in complex environments such as that beneath a bridge, but the complexity, cost, and time required for use of this method make it prohibitive in most cases. The use of more economical and less accurate methods may suffice as long as their limitations are understood and appropriately accounted for in the analytical process.
Methods to Reduce Traffic Speed in High-Pedestrian Rural Areas
Authors: Kamyab Ali , Andrle Steve , Kroeger Dennis , Heyer David S.
Published: April 2007

Many Minnesota counties are faced with the problem of high vehicle speeds through towns or resort areas that have significant pedestrian traffic. The impact of speed reduction strategies in high-pedestrian areas in rural counties of Minnesota was investigated. Speed data were collected at two selected study sites under their existing conditions ("no-treatment" or "before" condition) and after the proposed speed reduction strategies were installed. Second "after" data conditions were collected to study the short-term and long-term impact of the implemented strategies. The traffic-calming techniques employed at the Twin Lakes site consisted of removable pedestrian islands and pedestrian crossing signs. A dynamic variable message sign that sent a single-word message ("Slow") to motorists traveling over the speed limit was installed at the Bemidji site. The research study shows that the traffic-calming strategy deployed in Twin Lakes was effective in significantly reducing the mean speed and improving speed limit compliance in both the short term and long term. Despite proven effectiveness, the deployed speed reduction treatment in Bemidji Lake failed to lower the speed at the study site. The single-word message on the sign and the location of the sign, as well as a lack of initial enforcement, were the primary reasons for such failure.
How Well Can Child Pedestrians Estimate Potential Traffic Hazards?
Authors: Sarkar Sheila , Kaschade Christine , de Faria Fabio
Published: April 2007

An assessment was made of the perception skills and visual cues of schoolchildren in two schools where at least 50% of the children walk to and from school. This study, involving 79 schoolchildren, indicated that their current level of training to cross streets may not be sufficient for the prevalent traffic environments. Schoolchildren in the before-and-after school program were interviewed in July 2001. When shown a photograph of an intersection that was traversed by some of the children, about 90% forgot basic instructions about which directions they should look. Responses varied by gender, age, and school. A surprising 50% of schoolchildren who walked home either alone or accompanied did not know their home address. Of those driven to school, 41% had complete knowledge of their address. This study confirmed earlier findings that children may be overwhelmed by traffic complexity. The average overall score was 11.8 out of 18 (highest achievable score). The percentage of correct responses varied considerably, from less than 30% to the highest at about 50%. Children from the school near the intersections used for assessment performed better than the children who went to school farther away. A two-way average of variance of the overall score by age and school found a significant main effect of age and school. It was Age: F (2, 73) = 5.8, p < 0.004; School: F (1, 73) = 5.6, p < 0.021). More specific studies are warranted, but findings indicate that pedestrian safety education for children needs to offer more individualized and practical training to help them to respond to various hazards they are exposed to daily. More research is necessary pertaining to schoolchildren in urban areas where traffic patterns have become more complex and accommodations for children walking to school have not been modified.
Identifying Pedestrian High-Crash Locations as Part of Florida’s Highway Safety Improvement Program: A Systematic Approach
Authors: Espino Elio R. , Gonzalez Javier S. , Gan Albert
Published: April 2007

From 1997 to 2001, pedestrian fatalities represented 25.9% (2,065 fatalities) of all traffic fatalities in Florida. The latest available statewide crash data from the Florida Department of Highway Safety and Motor Vehicles reveals 8,487 pedestrian crashes, resulting in 510 deaths and 7,894 injuries, in 2001. However, a methodology is not currently available to identify pedestrian high-crash locations in Florida as part of the Highway Safety Improvement Program (HSIP). A study was conducted to provide the framework for the systematic identification of pedestrian high-crash locations on the state highway system as part of the HSIP. The study methodology uses the Poisson distribution to determine abnormally high pedestrian crash frequencies in a year for 1-mi roadway segments. Four-lane and six-lane divided roadways with continuous sidewalks on both sides of the road in Miami-Dade County were included. The crash data, the latest available from the crash database of the Florida Department of Transportation, correspond to the years 1997, 1998, and 1999. A χ2 goodness-of-fit test was performed to determine how well the data could be modeled by a Poisson process. The goodness-of-fit test was significant at the 2.5% level for the 1999 data, at the 10% level for the 1998 data, and less than 1% for the 1997 data. With a confidence level of at least 90%, a pedestrian crash frequency of three crashes in a 1-mi segment was found to be abnormally high for the fourlane divided facilities. For the six-lane divided facilities, four pedestrian crashes per 1-mi segment were established as the threshold value. From these threshold values, 22 1-mi segments were identified as pedestrian high-crash locations in Miami-Dade County for 1999.
Intersection Level of Service for the Bicycle Through Movement
Authors: Landis Bruce W. , Vattikuti Venkat R. , Ottenberg Russell M. , Petritsch Theodore A. , Guttenplan Martin , Crider Linda B.
Published: April 2007

The Florida Department of Transportation (DOT) has initiated multi-modal level-of-service (LOS) methodologies, including that for the bicycle travel mode. It has already adopted a bicycle LOS methodology for the roadway segment portion of the transportation network, the Bicycle Level of Service Model. Florida DOT’s ultimate goal is to develop corridor- and facilities-level LOS methodologies. Toward that goal, Florida DOT sponsored research to develop the first part of an intersection bicycle LOS methodology, the Intersection LOS for the bicycle through movement. This Intersection LOS for the bicycle through movement would provide a measure of the level of safety and comfort experienced by bicyclists riding through an intersection. The Intersection LOS model for the bicycle through movement is based on Pearson correlation analyses and stepwise regression modeling of approximately 1,000 combined real-time perceptions from bicyclists traveling a course through a typical U.S. metropolitan area’s signalized intersections. The study’s participants represented a cross section of age, gender, and geographic origin of the population of cyclists. Although further hypothesis testing is being conducted, the resulting general model for the Intersection LOS for the bicycle through movement is highly reliable, has a high correlation coefficient ( R2 = 0.83) with the average observations, and is transferable to the vast majority of U.S. metropolitan areas. The study reveals that roadway traffic volume, total width of the outside through lane, and the intersection (cross street) crossing distance are primary factors in the Intersection LOS for the bicycle through movement.
Refinement of Superpave High-Temperature Binder Specification Based on Pavement Performance in the Accelerated Loading Facility
Authors: Dongré Raj , D’Angelo John
Published: April 2007

Various parameters have been proposed to refine the current Superpave® high-temperature binder specification. One parameter relates the phase angle (δ) directly to accumulated strain from the creep–recovery test. Another variation suggests a formula to predict the accumulated strain using the current Superpave parameters G* and sin δ. Recently, NCHRP 9–10 project suggested a criterion based on a parameter derived from Burger’s viscoelastic model. In Europe, zero-shear viscosity is being proposed as a high-temperature specification parameter. These and other criteria proposed for high-temperature specification are evaluated by examining the correlation of each criterion to pavement performance. The experimental design consists of five asphalt binders used in the FHWA’s accelerated loading facility. Additionally, two binders used by the Nevada Department of Transportation in construction of 1–80 test sections were tested. Results show that the zero–shear viscosity correlates reasonably well with performance and is the best parameter among those evaluated. However, accurate determination of the zero-shear viscosity is time-consuming and requires expensive instrumentation, which makes it unsuitable as a specification parameter. Therefore, an easy method of obtaining zero-shear viscosity was evaluated and found to correlate to performance equally well. In this method, data from a single frequency sweep at the specification temperature are used to estimate the zero-shear viscosity. This method can be implemented immediately with little or no training or need for new instrumentation.
Prediction of Expected Red-Light-Running Frequency at Urban Intersections
Authors: Bonneson James A. , Son Ho Jun
Published: April 2007

Statistics consistently indicate that red-light running has become a significant safety problem throughout the United States. Comprehensive guidelines for treating red-light running at problem intersections have been developed. Unfortunately, these guidelines do not include a tool or technique for quantitatively determining if a problem exists and if a countermeasure is truly effective. The objective of this work is to describe the development and calibration of such a tool. The calibrated prediction model developed for this research indicates that red-light running increases with flow rate, speed, and dense platoons arriving at the end of the phase. It was also found that red-light running decreases with increasing cycle length and cross-street width, and when back plates are used on the signal heads. Uses for the calibrated model are described.
Safety Effects of Differential Speed Limits on Rural Interstate Highways
Authors: Garber Nicholas J. , Miller John S. , Yuan Bo , Sun Xin
Published: April 2007

To compare the safety effects of a uniform speed limit (USL) for all vehicles and a differential speed limit (DSL) for cars and heavy trucks, crash, speed, and volume data for rural Interstate highways for the period 1991 through 2000 were obtained from nine states. These states were divided into four policy groups based on the type of speed limit employed during the period: maintenance of a uniform limit only, maintenance of a differential limit only, a change from a uniform to a differential limit, and a change from a differential to a uniform limit. Statistical tests (analysis of variance, Tukey’s test, and Dunnett’s test) and the empirical Bayes method were used to study speed and crash rate changes in the four policy groups. The focus here is only on the statistical tests. The safety effects of DSL and USL were not different within the scope of the study. The mean speed, 85th percentile speed, median speed, and crash rates tended to increase over the 10-year period regardless of which type of speed limit was employed. When all sites within a state were analyzed, temporal differences in these variables were often not significant.
Examination of Fault, Unsafe Driving Acts, and Total Harm in Car-Truck Collisions
Authors: Council Forrest M. , Harkey David L. , Nabors Daniel T. , Khattak Asad J. , Mohamedshah Yusuf M.
Published: April 2007

Crashes involving large trucks and passenger cars are important topics for research and countermeasure development since they represent more than 60% of all fatal truck crashes and because the passenger car occupant is much more likely to be killed. This study ( a) examined “fault” in total car–truck crashes using North Carolina Highway Safety Information System (HSIS) data for comparison with fault analyzed in previous studies of fatal crashes, ( b) used general estimates system (GES) crash data to verify unsafe driving acts (UDAs) identified by expert panels in past studies, and ( c) used North Carolina HSIS data to identify critical combinations of roadway facility type, roadway location, and crash type based on “total harm”—a measure combining both the frequency and severity of the crash. Fault in total North Carolina car–truck crashes was found to differ significantly from past fatal crash studies, with the truck driver being at fault more often than the car driver both overall and in certain crash types. Car drivers continue to be at fault much more often in head-on and angle crashes. While it was not possible to analyze all UDAs identified in prior studies, when possible, the current analyses revealed differences between the GES crash data results and the expert-based results, pointing to the need for better UDA methods if they are to be used to target treatments. Finally, using the total-harm analysis with North Carolina car–truck crashes indicated that undivided rural arterials and collectors should be primary targets for further investigation and for treatment.
Methodology for Estimating Vehicle Miles Traveled for Commercial Motor Vehicles at the State Level
Authors: Brown Candace , Kennedy Nancy , Wright Don , Zak Walt
Published: April 2007

Described is one specific effort to better estimate commercial motor vehicle-related exposure at the state level in order to better determine commercial motor vehicle-related crash rates for state and federal programs. Limitations in the crash and exposure data affect the Federal Motor Carrier Safety Administration and a state’s ability to plan and assess operations and conduct ongoing analyses of program effectiveness. One important limitation has been the lack of reliable estimates of commercial motor vehicle exposure data at the state level. Exposure data, for the purpose of this report, are defined as the number of truck and bus vehicle miles traveled (VMT). Described is the methodology that was developed to calculate adjusted state VMT for commercial vehicles; results are presented for 1999 and 2000. The results support estimation of crash involvement rates for each state and provide exposure data for other analytical studies. The methodology to calculate adjusted state VMT for commercial motor vehicles has resulted in improved information resources in support of all crash analyses. The adjusted state VMT for commercial vehicles supports measurement of program effectiveness and development of countermeasures to promote motor carrier safety. The adjusted state VMT for commercial motor vehicles methodology and the commercial vehicle fatal-crash involvement rate reports enable state and federal agencies to better focus their safety programs and enforcement resources.
Model of Household Trip-Chain Sequencing in Emergency Evacuation
Authors: Murray-Tuite Pamela M. , Mahmassani Hani S.
Published: April 2007

An evacuation modeling framework that bridges the gap between observed household behavior and traditional evacuation models is presented. Numerous observers have noted that household members seek each other and then evacuate as a single unit. The desire to find relatives before leaving an area may result in people moving toward the danger instead of away from it. This pattern has not been captured by traditional evacuation models, which assume that people immediately move away from the danger. The gap between observed behavior and theoretical models leads to longer-than-expected evacuation times. A series of two linear integer programs provide an expression for the household behavior in evacuation conditions. The first formulation determines the meeting location for the household members. The second formulation determines which drivers pick up each of the family members and the sequence of the collection. Tying these linear programs to traffic simulation software allows for a more complete evacuation simulation. Furthermore, information supply strategies may be incorporated into the simulation. The effect of information on reassignment and resequencing may also be examined.
Systematic Investigation of Variability due to Random Simulation Error in an Activity-Based Microsimulation Forecasting Model
Authors: Castiglione Joe , Freedman Joel , Bradley Mark
Published: April 2007

A key difference between stochastic microsimulation models and more traditional forms of travel demand forecasting models is that micro-simulation-based forecasts change each time the sequence of random numbers used to simulate choices is varied. To address practitioners’ concerns about this variation, a common approach is to run the microsimulation model several times and average the results. The question then becomes: What is the minimum number of runs required to reach a true average state for a given set of model results? This issue was investigated by means of a systematic experiment with the San Francisco model, a microsimulation model system used in actual planning applications since 2000. The system contains models of vehicle availability, day pattern choice, tour time-of-day choice, destination choice, and mode choice. To investigate the variability of the forecasts of this system due to random simulation error, the model system was run 100 times, each time changing only the sequence of random numbers used to simulate individual choices from the logit model probabilities. The extent of random variability in the model results is reported as a function of two factors: ( a) the type of model (vehicle availability, tour generation, destination choice, or mode choice); and ( b) the level of geographic detail—transit at the analysis zone level, neighborhood level, or countywide level. For each combination of these factors, it is shown graphically how quickly the mean values of key output variables converge toward a stable value as the number of simulation runs increases.
Temporal-Spatial Microassignment and Sequencing of Travel Demand with Activity-Trip Chains
Authors: Abdelghany Ahmed F. , Mahmassani Hani S.
Published: April 2007

A stochastic temporal–spatial microassignment and activity sequencing model for activity–trip chains is presented. In this model, trip-chain patterns are defined by the respective locations of destinations in the chain, preferred arrival times at these destinations, and the activity durations at the intermediate destinations; they are given as input to the model. A stochastic dynamic user equilibrium problem is formulated and solved for this purpose. In this problem, drivers simultaneously seek to determine their departure time, route choice, and sequence of their intermediate activities at the origin to minimize their perceived travel cost. This perceived cost is typically a function of the travel time and the schedule delay at the intermediate and final destinations. The model is presented through a study of the relative efficiency of carpooling and trip-chaining travel behavior in a network context. In that example, the performance of travelers who have the option to carpool and chain trips is compared with that of households with single-occupant and individual trip-based travel. Several measures of travel performance, including travel distance, travel time, and schedule delay, are considered for that comparison.
Empirical Analysis of Commute Stop-Making Behavior
Authors: Chu You-Lian
Published: April 2007

A set of stop frequency models used to predict the number of nonwork activity stops made by individual adult workers on their way to work (home-based morning commute), their way home from work (home-based evening commute), and during their working hours (work-based midday travel) is presented. The ordered probit formulation was used to account for the ordered classification scale of the dependent variable (in this case, number of stops—zero stop, one stop, and two or more stops). With the New York Metropolitan Transportation Council household interview data, the models were used to examine commute stop-making behavior for individual workers residing in New York City (including the boroughs of Manhattan, Brooklyn, Queens, Bronx, and Staten Island). The empirical results provide useful insights into the effects of sociodemographics, land use density, transportation service, and work schedule on commute stop-making propensity in a highly urbanized environment. The findings also provide exploratory methodological evidence that could lead to an approach for predicting the change in commute stop-making propensity as a result of the changes in sociodemographic conditions and transportation-land use scenarios.
Estimation of Origin-Destination Matrices: Relationship Between Practical and Theoretical Considerations
Authors: Aerde Michel Van , Rakha Hesham , Paramahamsan Harinarayan
Published: April 2007

A comprehensive overview of the entire class of formulations and most recognized solutions for estimating origin–destination (O-D) demand tables is presented. Specifically, trip distribution formulations are compared with less-known synthetic O-D estimation solution techniques. It is demonstrated that the trip distribution gravity model is nothing but a subset of the maximum-likelihood solution to the synthetic O-D problem. Finally, a numerical solution to the maximum-likelihood synthetic O-D problem is proposed that overcomes the shortcomings of the state-of-practice formulations. The proposed solution, which has been implemented in QueensOD software, does not require flow continuity at the network nodes, as is the case for most formulations. The latest version of QueensOD can be shown to yield results consistent with standard equation solvers (Excel and MATLAB) and with exhaustive enumeration, for small networks, for which all three methods are feasible. However, QueensOD has also been applied to networks with more than 1,000 zones and 5,000 links on a personal computer, typically requiring no more than 1 h to solve problems of this size. The solutions obtained by QueensOD reflect multipath routings, consider correctly that the total number of trips in the network may not be constant, and properly reflect the role of the seed matrix. The model can also be applied to deal with problems in which the routes are not known a priori.
Reverse-Engineered Land Use Patterns to Minimize Congestion
Authors: Bose Amica , Fricker Jon D.
Published: April 2007

A neighborhood land use pattern designed to accommodate the most frequently taken nonwork trips within an acceptable distance from home was developed. Instead of starting from a specified set of land uses and studying the travel characteristics, mixed land use patterns that fit the observed trip-making behavior of people were formulated. The result is called a reverse-engineered neighborhood, or REN. The REN was tested against a Euclidean development that had separated land uses. Results show a substantial reduction in nonwork trip lengths (in terms of both travel time and distance) in the REN compared with the Euclidean development. The efficiency of the REN is the result of having more trip destination choices available to residents at acceptable distances. The procedures in the analysis are described and demonstrated, the results of the analysis are presented, and directions for further study are suggested.
Assessing Impact of Urban Form Measures on Nonwork Trip Mode Choice After Controlling for Demographic and Level-of-Service Effects
Authors: Rajamani Jayanthi , Bhat Chandra R. , Handy Susan , Knaap Gerritt , Song Yan
Published: April 2007

The relationship between travel behavior and the local built environment remains far from entirely resolved, despite several research efforts in the area. The significance and explanatory power of a variety of urban form measures on nonwork activity travel mode choice have been investigated. The travel data used for analysis are from the 1995 Portland Metropolitan Activity Survey conducted by Portland Metro. The database on the local built environment was developed by Song in 2002 and includes a more extensive set of variables than previous studies that have examined the relationship between travel behavior and the local built environment by using the Portland data. The results of the multinomial logit mode choice model indicate that mixed uses promote walking behavior for nonwork activities.
Transportation’s Influence on Land Use Development: Historical Spatial-Temporal Approach
Authors: Woudsma Clarence , Jensen John F.
Published: April 2007

The interrelationships between transportation and land use remain contentious despite extensive research. In particular, the influence of transportation system performance on land use development, although recognized as a lagged relationship, has yet to be fully understood. The existing methodological approaches are critically evaluated, and support for the development of a novel historical spatial–temporal approach is provided. The uniqueness of this approach is based on the creation, modification, and analysis of extensive historical databases (1964 to 1998) of transportation system performance (annual weekday traffic volumes) and microscale parcel level data (land use, actual use, and year of development) for the city of Calgary. All data are in yearly time steps, stored within a geographic information system (GIS) framework. Both data sets are significantly modified to create ( a) a congestion index based on volume/capacity ratios and ( b) development intensity and rates of change based on existing transportation zones. An example focus is on warehousing and logistics land uses, which are critically important to the city’s economy and broadly underexamined within the field. Methods used include scientific visualization, correlation analysis, and the use of GIS spatial analytical approaches. The results support the appropriateness of the data modifications and exemplify the value of scientific visualization. At a systemwide level, the timing and location of warehousing and logistics development are found to be statistically associated with high-congestion areas. For individual transportation zones, the relationship between developments and zone proximal congestion is less clear, although there is weak evidence for the existence of lagged effects.
How Density and Mixed Uses at the Workplace Affect Personal Commercial Travel and Commute Mode Choice
Authors: Chatman Daniel G.
Published: April 2007

A high density of shops and services near the workplace may make it easier to carry out personal commercial activities on foot before, during, and after work, enabling reduced vehicle use during the rest of the day. Investigating this question is an important addition to the current research, which has focused on residential neighborhoods. Data from the 1995 Nationwide Personal Transportation Survey are used to investigate the influence of workplace employment density and share of retail employment on commute mode choice and vehicle miles traveled (VMT) to access personal commercial activities. The analysis controls for socioeconomic characteristics and accounts for the endogeneity of commute mode choice and personal commercial VMT by employing a joint logit-Tobit model. Employment density at the workplace is found to be associated with a lower likelihood of automobile commuting and reduced personal commercial VMT, while the presence of employment in the retail category does not play a significant role. Workplace density is more clearly related to reduced VMT and automobile commuting than to characteristics of workers’ residential neighborhoods and could have significant influences on personal commercial VMT and automobile commuting when increasing over a large area. The results suggest that land use planners should focus on encouraging employment density to a greater extent than is the current practice, although further research is needed on the role played by correlated factors such as higher parking costs, increased road congestion, and better transit service.