bluuebunny/crossref_metadata_2025 huggingface dataset:
Establishing Linear Viscoelastic Conditions for Asphalt Binders
Authors: Marasteanu Mihai O. , Anderson David A.
Published: April 2007

The linear viscoelastic regime is defined in terms of the constitutive relationship between the stress and the strain. The set of equations that define the fundamental linear viscoelastic material properties in the time and frequency domains and their relationship to one another is based on the validity of the linearity principle. A material must obey two simultaneous conditions to be linear viscoelastic: the homogeneity (also called proportionality) condition and the superposition principle. On the basis of these considerations a testing procedure was developed to check linear viscoelastic conditions for tests performed on asphalt binders with the dynamic shear rheometer (DSR), the bending beam rheometer (BBR), and direct tension (DT). The testing procedure for the DSR requires performing strain sweeps and multiwave single-point tests. For the BBR, tests performed using different constant loads are required. In addition, the recovery part of the specification test is recorded. For the DT, tests performed at different strain rates and relaxation tests performed at different strain levels are required. When applied to asphalt binder data, the testing procedure found no departure from viscoelastic conditions for the DSR and BBR test data. However, the DT procedure indicated a departure from linear viscoelastic conditions.
Bus Rapid Transit Technologies in the Americas: An Overview
Authors: Diaz Roderick B. , Schneck Donald C.
Published: April 2007

Results from a survey of international bus rapid transit (BRT) systems reveal a wide range of technology options for implementing a BRT system. Eight BRT systems (seven existing and one under development) in North and South America demonstrate innovative applications of five bus technology components—vehicles, guideways and stations, control systems (dispatching and signaling), fare systems, and passenger information systems. These innovative applications, combined with fundamental changes in operating plans and the customer interface, provide a mode distinct from conventional bus transit. This preliminary phase of the survey found that guideway improvements are the most common strategy to move from conventional to rapid transit service. Innovations in vehicle design, control system technology, and fare system technology are also commonly used. All the surveyed systems demonstrate isolated innovation in passenger information systems technology. These technology applications were primarily directed toward improving the speed, reliability, and user-friendliness of service.
Car Ownership Dynamics Seen Through the Follow-Up of Cohorts: Comparison of France and the United Kingdom
Authors: Dargay Joyce M. , Madre Jean-Loup , Berri Akli
Published: April 2007

The dynamics of car ownership based on age-cohort data constructed from repeated cross-section surveys is investigated for France and the United Kingdom, both nationally and for different geographic areas. Two different modeling strategies are used: a demographic approach and a dynamic econometric approach. The demographic approach is primarily oriented toward long-term forecasting. It takes into account changes in car ownership over the life cycle for each generation, differences between generations, and period effects explained by income and prices. The dynamic econometric approach is mainly concerned with estimating the elasticity of car ownership with respect to income and prices in the short and long run. It is based on a dynamic model in which household car ownership is specified as a function of income, prices, sociodemographic factors, and previous car ownership. The results using the two approaches are quite similar. The income elasticity is significantly higher in the United Kingdom than in France, is higher in rural than in urban areas, and decreases over time as car ownership increases. Generation gaps, which have been important between older generations, are not significant for households whose head was born after the 1940s, which implies that the diffusion of car ownership over generations is nearing completion. In addition, a declining income elasticity confirms a progressive evolution toward saturation. Finally, car ownership is considerably more sensitive to car purchase prices than to gasoline prices and both appear to be more significant in densely populated zones than in rural areas.
Effect of Route Choice Models on Estimating Network Capacity Reliability
Authors: Chen Anthony , Tatineni Maya , Lee Der-Horng , Yang Hai
Published: April 2007

The issue of planning for adequate capacity in transportation systems to accommodate growing traffic demand is becoming a serious problem. Recent research has introduced "capacity reliability" as a new network performance index. Capacity reliability is defined as the probability that a network can accommodate a certain volume of traffic demand at a required service level given variable arc capacities, while accounting for drivers' route choice behavior. Previous papers on this topic provide a comprehensive methodology for assessing capacity reliability along with extensive simulation results. However, an important issue that remains is what type of route choice model should be used to model driver behavior in estimating network capacity reliability. Three different route choice models (one deterministic and two stochastic models) are compared, and the effect of using each of these models on estimating network capacity reliability is examined.
Developing a Dynamic Traffic Management Modeling Framework for Hurricane Evacuation
Authors: Barrett Bridget , Ran Bin , Pillai Rekha
Published: April 2007

Evacuation is becoming increasingly difficult as the population of hurricane-prone regions continues to grow dramatically. In addition, development in coastal communities in the United States is expected to continue to greatly outpace new construction and improvements to the highway infrastructure. Consequently, there is a great need for hurricane evacuation models, which allow emergency response personnel to develop effective evacuation plans and management strategies. The development of a dynamic hurricane evacuation modeling framework is described, which can be used for long-term and short-term planning purposes as well as for real-time operational purposes.
Enhancing Transit Circulation in Resort Areas: Operational and Design Strategies
Authors: Thrasher Susan A. , Hickey Thomas R. , Hudome Robert J.
Published: April 2007

Many resort areas and other major activity centers are facing transportation challenges as rising traffic congestion erodes the quality of a visitor’s experience. Many resort areas have turned to public transportation as an alternative strategy for visitor circulation, but these services often become enmeshed in the same traffic jam that they were intended to circumvent. The city of Virginia Beach, Virginia, undertook an aggressive, long-term effort to establish and enhance an effective transit circulation in its beachfront resort area through a combination of physical design improvements and operational management. The development and implementation of the combination strategy are described, and lessons learned that are relevant to other resort-area transit-circulator services are outlined.
Cincinnati’s New Riverfront Transit Center: Unique Approach to Serving the Midwest’s Largest Sports and Entertainment Venue
Authors: Reynolds Timothy J.
Published: April 2007

The Southwest Ohio Regional Transit Authority of Cincinnati is developing the new Riverfront Transit Center to serve special events and attractions that are being developed along the city’s central riverfront. The $42 million facility is scheduled to be fully operational in 2003. The two stadiums are part of an ambitious riverfront renewal plan that will result in the Midwest’s largest sports and entertainment complex. The facility also will feature two new stadiums for professional baseball and football, an existing indoor arena, a new 14-ha (35-acre) festival park and concert venue, and the Freedom Center, a major museum commemorating the Underground Railroad. The Riverfront Transit Center is an integral part of the redesign of a 1.6-km (1-mi) segment of Interstate 71, which currently separates downtown Cincinnati from the Ohio River. The facility will include 20 sawtooth bus bays and two passing lanes to allow the movement of 20,000 passengers/h. By 2010, an estimated 375,000 passengers/year will use the transit center. In addition to being used for special events, the facility will be used on a daily basis by charter buses serving the Freedom Center.
Integrated Smart-Card Fare System: Results from Field Operational Test
Authors: Giuliano Genevieve , Moore James E. , Golob Jacqueline
Published: April 2007

Evaluation results of the Ventura County smart card Phase III field demonstration are presented to show the feasibility of using smart cards and other technology to provide an integrated fare medium across several transit operators. The evaluation addressed technical performance, user response, and institutional issues. Technical performance was affected by installation problems, equipment failures, and communications problems. Technical problems often were the outcome of institutional issues. Smart-card users were very satisfied with the new fare medium; however, transit patrons in Ventura County have very low incomes, many are not English speaking, and few transit users bought and used the cards. Overall, the demonstration suffered from the absence of clear roles and responsibilities as well as a lack of understanding of the complexity and demands of the technology.
Chicago Transit Authority Weekday Park-and-Ride Users: Choice Market with Ridership Growth Potential
Authors: Foote Peter J.
Published: April 2007

Chicago Transit Authority (CTA) park-and-ride users make up a small but important submarket of CTA ridership (2.3 million of 445.3 million annual rides). In fall 1998, a survey was made of 1,758 CTA park-and-ride users on weekdays at 15 CTA park-and-ride lots near the point of payment. The survey asked for customer satisfaction ratings, travel characteristics, prior mode used, reasons for park-and-ride use, demographics, and, at the largest lots, ratings of the desirability of potential amenities or services that could be added to the lots. Compared with CTA riders overall, park-and-ride users showed substantially higher household incomes and travel frequencies and made predominantly work-related trips to and from Chicago’s central business district. Riders said that they chose to use park-and-ride because it was the fastest way to make their trip, because of the cost of parking at their destination (mean cost of $10.29), or because they disliked driving. Before using CTA park-and-ride service, most customers used some automobile-related means of making their trips. Substantial turnover and geographic information system analysis of home location data suggest that regular target marketing and investment in new facilities would have a positive impact on overall ridership. Of potential customer amenities tested, riders showed the most willingness to try shopping-related amenities (convenience mart, fast food and grocery outlet) over amenities related to automobile servicing.
Lateral Load Capacity and Passive Resistance of Full-Scale Pile Group and Cap
Authors: Rollins Kyle M. , Sparks Andrew E. , Peterson Kris T.
Published: April 2007

Static and dynamic (statnamic) lateral load tests were performed on a full-scale 3 × 3 pile group driven in saturated low-plasticity silts and clays. The 324-mm outside diameter steel pipe piles were attached to a reinforced concrete pile cap (2.74 m square in plan and 1.21 m high), which created an essentially fixed-head end constraint. A gravel backfill was compacted in place on the back side of the cap. Lateral resistance was therefore provided by pile-soil-pile interaction as well as by base friction and passive pressure on the cap. In this case, passive resistance contributed about 40 percent of the measured static capacity. The measured resistance was compared with that computed by several techniques. The log-spiral method provided the best agreement with measured resistance. Estimates of passive pressure computed using the Rankine or GROUP p-y curve methods significantly underestimated the resistance, whereas the Coulomb method overestimated resistance. The wall movement required to fully mobilize passive resistance in the dense gravel backfill was approximately 0.06 times the wall height, which is in good agreement with design recommendations. The p-multipliers developed for the free-head pile group provided reasonable estimates of the pile-soil-pile resistance for the fixed-head pile group. Default p-multipliers in the program GROUP led to a 35 percent overestimate of pile capacity. Overall dynamic resistance was typically 100 to 125 percent higher than static; however, dynamic passive pressure resistance was over 200 percent higher than static.
State of the Practice for Design of Groups of Laterally Loaded Drilled Shafts
Authors: Walsh Kenneth D. , Fréchette Daniel N. , Houston William N. , Houston Sandra L.
Published: April 2007

Many state departments of transportation (DOTs) are beginning to use a larger percentage of drilled shafts for their deep foundations. Therefore, a clear understanding of current design methodology and specifications is important. The three most common design methods in use today are the group reduction factor, the p-multiplier method, and the modulus of subgrade reaction multiplier. A brief discussion of each method is presented. Telephone interviews were conducted with state DOTs to determine their current design procedure for groups of laterally loaded drilled shafts. Responses were obtained from all 50 states. Additional interviews were conducted with several well-known researchers in the field of deep foundations to determine what procedure they recommend. From these interviews it was clear that there is no uniformity in design methods or even in interpretation of the AASHTO recommendations for laterally loaded drilled shaft groups. The different interpretations of the AASHTO recommendations may be due to wording used in the AASHTO specifications, namely, the “ratio of lateral resistance of shaft in group to single shaft.” It is somewhat unclear as to whether this wording refers to the single-pile capacity or to the soil resistance. To understand the intended method of application of these factors, a historical search of the literature was conducted. It is clear that the source cited in the AASHTO specifications recommended using the reduction factors to reduce the modulus of subgrade reaction.
Evaluating Horizontal Alignment Design Consistency of Two-Lane Rural Highways: Development of New Procedure
Authors: McFadden John , Elefteriadou Lily
Published: April 2007

Design consistency refers to the condition wherein the roadway geometry does not violate driver expectations. Operating-speed profile models are used to evaluate the consistency of a design by identifying locations with large speed variability between successive design elements. There is a direct correlation between safety and variability in speeds. Recent operating-speed models predict the 85th percentile speeds on horizontal curves and compare this value with the expected 85th percentile speed on the approach tangent. There is a direct correlation between speed variability between successive design elements and crash rates. Eighty-fifth percentile speeds, however, do not necessarily represent the speed reductions experienced by drivers. The primary objective of the research was to assess the efficacy of the use of 85th percentile speed by operating-speed profile models to evaluate the consistency of a design. Speed data were collected at 21 horizontal curve sites. These data were used to evaluate the implication of using 85th percentile speed for evaluating design consistency. A new parameter was investigated for analyzing design consistency: the 85th percentile maximum reduction in speed (85MSR). This parameter is calculated by using each driver’s speed profile from an approach tangent through a horizontal curve and determining the maximum speed reduction each driver experiences. These maximum speed reductions are sorted, and the 85th percentile value becomes the statistic of interest, or 85MSR. 85MSR was compared with the difference in 85th percentile speeds (85S), and it was found that 85MSR is significantly larger than 85S. The data showed that, on average, 85MSR is approximately two times larger than 85S. Models were developed that predict 85MSR as a function of geometric design elements, and these models could be used to complement existing operating-speed models.
Analyzing Influence of Geometric Design on Operating Speeds Along Low-Speed Urban Streets: Mixed-Model Approach
Authors: Poe Christopher M. , Mason John M.
Published: April 2007

Studies have documented the significant effect of horizontal curvature on operating speed on two-lane rural highways. The geometric design of these facilities emphasizes the forgiving roadside to accommodate the higher vehicular speeds. High-speed geometric design is predicated on selecting design values for geometric elements that promote speed consistency and safety. The low-speed environment has different objectives in trying to provide access and accommodate multiple roadway users, such as bicyclists and pedestrians. The goal is to maintain lower speeds and thus to achieve the functionality of the roadway and improve overall safety. Too often, the speeds on these facilities exceed the intended target speed of the roadway. A study conducted by the Pennsylvania Transportation Institute supported several research efforts in the low-speed environment. Presented is a more sophisticated analysis of low-speed urban street data using mixed models. A mixed-model statistical approach with repeated measures is used to analyze the influence of geometric elements on operating speed. The power of a mixed-model approach is that it accounts for the random effect in the database (such as the data collection sites themselves) while modeling the fixed geometric effects. Because data were collected at several points along each roadway, the analysis also applies a repeated-measures approach that addresses the geometric elements effect on the same subjects traversing a roadway. The advantages and disadvantages of applying a more sophisticated statistical approach are presented.
Speed-Profile Model for Two-Lane Rural Highways
Authors: Fitzpatrick Kay , Collins Jon M.
Published: April 2007

Design consistency refers to highway geometry’s conformance with driver expectancy. Generally, drivers make fewer errors at geometric features that conform with their expectations. A proposed method for evaluating design consistency is to predict the speed along an alignment by using a speed-profile model. A speed-profile model was developed by using the following: speed prediction equations that calculate the expected speed at horizontal, vertical, or combination curves; assumed desired speed for the roadway; TWOPAS equations that determine the performance-limited speeds at every point; acceleration and deceleration rates; and several documented assumptions. The speed-profile model can be used to evaluate the design consistency of a facility or to generate a speed profile along an alignment. In conclusion, the speed-profile model developed appears to provide a suitable basis for the Interactive Highway Safety Design Model design consistency module.
Effects of Right-Turn Lanes on Driveway Sight Distance
Authors: Zeidan George R. , McCoy Patrick T.
Published: April 2007

Vehicles entering a driveway from an exclusive right-turn lane may restrict the sight distance available to vehicles waiting to enter the arterial street from the driveway. The sight distance available to the vehicles waiting at a driveway is a function of the geometric design of the driveway and the right-turn lane. The relationship between available sight distance and the relevant geometric design variables is examined. The analysis identifies geometries that provide adequate sight distances for various design speeds.
Likely Users of Advanced Traveler Information Systems: Evidence from the Seattle Region
Authors: Raj Mehndiratta Shomik , Kemp Michael A. , Lappin Jane E. , Nierenberg Eric
Published: April 2007

Findings about the claimed use of and interest in traveler information systems among segments of the general population in the Seattle metropolitan region are reported. The research is based on data collected from a 1997 intelligent transportation system supplement to the Puget Sound Regional Council’s transportation panel travel diary study. In general, interest in traffic information was found to be a function of complex travel behavior, demographics, and factors related to attitudinal and technology interest. It was also found that the potential market for advanced traveler information systems (ATIS) includes several market segments with different needs; each is drawn to ATIS for distinct and varying reasons. First, the so-called control seeker segment includes people who desire greater than average control over their environment. In a traffic information context, that translates to better knowledge of their travel times, especially in congested travel environments. The second segment of interest, dubbed webheads, includes individuals who are very comfortable with high technology, and it is possible that they would be drawn to ATIS at least partially through specific high-technology dissemination media. A third segment is made up of individuals who are less comfortable with (or less interested in) technology and are primarily interested in pretrip information, which they use to make departure time and route choice decisions.
Fast Emergency Vehicle Preemption Systems
Authors: Shibuya Shuetsu , Yoshida Toshihiro , Yamashiro Zuiki , Miyawaki Makoto
Published: April 2007

In an automotive society that increasingly depends on cars, the National Police Agency is tackling the problem of operation support of emergency vehicles for incidents, accidents, and other emergency cases in order to manage traffic appropriately. This support of emergency vehicle operations is considered to be one of nine developing fields in Japan’s intelligent transportation systems. Recently, to deal with an increasing crime rate, a growing number of accidents, and problems with the elderly, more and more emergency vehicles are being dispatched. Against this background, it is indispensable for the police administration, as the manager of traffic and as an important instrument for maintaining peace and order, to help emergency vehicles in urgent situations reach the scene at the earliest possible moment and to prevent accidents during operations. Fast emergency preemption systems have a two-way communication function through the use of an infrared beacon, which is the key infrastructure of a traffic control system. Such a system supports the operation of emergency vehicles in a safe and effective manner by using route guidance and priority signal control; it also warns civilian vehicles about approaching emergency vehicles.
Fifty Years of TRB Bridge Committees
Authors: Viest I. M. , Siess C. P.
Published: April 2007

The first bridge committee in the Highway Research Board was organized in 1949 in the Department of Highway Design. Today, 11 TRB committees deal with bridges and related structures. Historical development of the organization of bridge committees is described first. Discussion of their accomplishments follows under the headings of annual meetings, publications, research, conferences, and management workshops. It is concluded that TRB bridge committees serve today as the principal catalyst for bridge research in the United States.
Seismic Performance of Timber Bridges
Authors: Mander John B. , Allicock Dion R. , Friedland Ian M.
Published: April 2007

Compared with the seismic performance of concrete and steel highway bridges, the seismic performance of timber bridges is not well understood. This is because, historically, little effort has been spent on documenting the seismic performance of timber bridges in past earthquakes or conducting research to develop an improved understanding of the seismic design or retrofit requirements for timber bridges. Research work sponsored by FHWA and conducted at the University at Buffalo in conjunction with the Multidisciplinary Center for Earthquake Engineering Research to ( a) document the seismic performance of timber bridges in past earthquakes, ( b) experimentally assess the strength and ductility capabilities of timber pile substructures, and ( c) conduct a seismic vulnerability analysis of timber bridges (principally with shaking in the longitudinal direction) to assess the expected modes of failure is presented. Finally, with a particular emphasis on the 1964 Alaska earthquake, conclusions demonstrating why certain types of behavior lead to failures in timber bridges are drawn.
New Techniques in Difficult Ground Tunneling
Authors: Ressi di Cervia Arturo
Published: April 2007

The construction of tunnels under soft ground conditions has been solved by the use of special technologies and equipment. This equipment opens new possibilities for the enlargement of existing tunnels while maintaining traffic flow. The work can be done safely and economically even under the most difficult soil conditions. Two new tunneling techniques for the full-face excavation of galleries under difficult ground conditions and one new technique for cut-and-cover tunnel excavation are described.
Application of Benefit-Cost Analysis to the Proposed California High-Speed Rail System
Authors: Brand Daniel , Kiefer Mark R. , Parody Thomas E. , Mehndiratta Shomik R.
Published: April 2007

A high-speed rail system operating on a dedicated right-of-way that results in a significant volume of trips being diverted from the air and highway modes can be expected to generate significant benefits. The major benefits that will accrue to both users and nonusers from the construction and operation of such a system are described. Both intercity and urban travel benefits are included in the analysis. A methodology for how these diverse benefits can be quantified is presented, and, importantly, it is shown how these benefits can be monetized for input into a comprehensive benefit-cost analysis. Of the 11 types of benefits examined, 4 were found to produce the bulk of the benefits of the high-speed rail system. For the present purposes, benefit-cost analysis is a public-sector evaluation tool that compares all the benefits of a project to society with all the costs of a project. The objective is to ascertain whether all the benefits do in fact exceed all the costs. The major benefits include the revenues derived from high-speed rail users, the high-speed rail user benefits (consumer surplus) net of fares paid, the travel time savings to urban commuters, and the value of time savings to intercity air travelers. Actual data have been taken from the proposed California highspeed rail system to illustrate the benefits that can be expected from such a system and the discrete steps that have been undertaken in the benefit-cost analysis.
Railroads in Greece: History, Characteristics, and Forecasts
Authors: Paravantis John A. , Prevedouros Panos D.
Published: April 2007

Greece was relatively tardy in implementing a national rail network. The Greek Railways Organization (OSE) was formed in 1970 and united a number of regional railroads, some dating back to 1884. The current rail network in Greece has a length of approximately 2500 km with standard- and metric-gage tracks. Disadvantages of the network include a high percentage of single-line track, lack of homogeneity of track gage, inefficient alignment, absence of intermodal connections, and many at-grade intersections. Advantages include double tracks in a significant part of the Athens-Thessalonica axis that serves more than half of Greece’s population, improved operational controls, and popular intercity trains offering speedy service. Factors that affect railroad passenger and freight volumes include competition from airlines and motor carriers, gas prices, inflation, and the gross national product. These factors were used to estimate time-series models. Forecasts indicate increasing passenger demand and decreasing freight demand. OSE could provide a valuable and viable passenger service if cost-effective expenditures for improving it are possible. The future of freight operations is not hopeful. Additional emphasis may be placed on lines with historical and cultural significance. Further study is needed to assess the sustainability of forecasts vis-à-vis actual market shares and costs.
Concrete Slab Track State of the Practice
Authors: Tayabji Shiraz D. , Bilow David
Published: April 2007

Railway track technology has evolved over a period of 150 years since the first railroad track on timber ties was introduced. For much of this period, the conventional track system, commonly referred to as the ballasted track system, has consisted of certain components including rails, ties, ballast, and the subgrade (roadbed). Over the last 20 years, there has been an increase in the use of concrete slab technology for transit, commuter, and high-speed train applications. Essentially, a slab track consists of a concrete slab placed on a subbase over a prepared subgrade. The rails may be directly fastened to the concrete slab, or the rails may be placed on concrete blocks or another slab system that is placed on (or embedded in) the underlying concrete slab. A version of the slab track, developed in the Netherlands, incorporates rails embedded in a trough in the slab and surrounded by elastomeric material. The slab track systems for passenger service applications incorporate several requirements to mitigate noise and vibration. The slab track system for transit applications in the United States and for high-speed rail in Europe and Japan has performed well over the last 20 years. Also, the limited application of the slab track system for mixed passenger service-freight operations has also exhibited good performance. Because of the continued increase in gross tonnage expected to be carried by railroads and the expected growth in high-speed passenger rail corridors, with the smaller deviation in the rail geometry allowed for high-speed rail, the need for a stronger track structure is apparent. At-grade concrete slab track technology is expected to fill the need for stronger track in the United States. The state of the practice related to concrete slab track technology is summarized.
Prospects for Increasing Average Aircraft Size at Congested Airports
Authors: Gosling Geoffrey D. , Hansen Mark M.
Published: April 2007

It has been common for airport traffic forecasts to assume a continuing increase in average aircraft size in the future so that the anticipated growth in passenger demand will not result in a proportional increase in aircraft operations. However, to understand the likely future trends in average aircraft size, as well as strategies that an airport might pursue to encourage airlines to use larger equipment, it is necessary to understand the competitive dynamics of the various markets served by the airport and the factors that determine the size of equipment that airlines will use in those markets. Recent trends in average aircraft size at a major U.S. West Coast airport and the influence of market characteristics on the size of aircraft used in different markets are examined. The changes in the past decade in selected short- and medium-haul markets are analyzed, and the results are presented of a cross-sectional model that estimates the influence of various market characteristics, including air traffic delay levels, on the average size of aircraft deployed in a wide variety of markets throughout the United States. The prospects for airport capacity constraints to influence airlines to make use of larger aircraft are discussed, and the implications for airport strategies to encourage the use of larger aircraft are examined.
Measuring the Level of Services at Airport Passenger Terminals: Comparison of Perceived and Observed Time
Authors: Yen Jin-Ru , Teng Chung-Hsiang , Chen Peter S.
Published: April 2007

A mathematical model to measure the level of service at airport passenger terminals is presented. The model relates passengers’ ratings of services at terminals and the time spent waiting for those services. The fuzzy concept is used to deal with the vagueness of service ratings such as “satisfied” and “unsatisfied.” Furthermore, two instruments are used to obtain the amount of time spent in service processes: perceived time reported by passengers and objective quantities measured by researchers. Empirical data reveal that the mean of perceived waiting/service time is significantly greater than the objective time in both check-in and baggageclaim processes, indicating that passengers tend to overestimate their time spent in each process. Furthermore, the amount of overestimation varies among service processes, with passengers having greater overestimations in both check-in service and baggage-claim waiting than in check-in waiting. These results imply that the two former processes are less tolerable than the latter one. The differences between those two measurements are further accentuated by the estimated level-of-service thresholds, with most thresholds based on subjective perceptions being greater than those based on objective measures. Estimation results also suggest that airport operators and airlines need more efforts to upgrade a service currently at higher service levels than at lower service levels.
Estimating Capacity of Europe’s Airspace Using a Simulation Model of Air Traffic Controller Workload
Authors: Majumdar Arnab , Polak John
Published: April 2007

The growth in European air traffic has led to delays, inefficiencies, and attendant costs. This growth is predicted to increase. The workload of the air traffic controller is the limiting factor in airspace capacity and will remain so despite the introduction of new technology and procedures. A framework is provided for modeling airspace capacity by considering the factors that affect controller workload and then using a model of controller workload, aided by the appropriate analytical techniques, to estimate airspace capacity. The context of the current European air traffic control problems is given, airspace capacity is examined, and a scheme is outlined for estimating airspace capacity using simulation modeling. The Reorganized ATC Mathematical Simulator (RAMS) controller workload model was chosen for use in the research. The output of this simulation model is used for estimating airspace capacity, and simulation experiments undertaken using RAMS are described. The analysis of how these factors affect the air traffic controller, using a generalized linear modeling framework, is undertaken. This accounts for the spatial correlation structure of the error structure. Two alternative estimation methods are used: maximum likelihood and estimated generalized least squares. The results from the analysis, together with a workload-based capacity measure, are used to provide airspace capacity estimates.
Short-Term Delay Mitigation Strategies for San Francisco International Airport
Authors: Eads George C. , Kiefer Mark R. , Mehndiratta Shomik
Published: April 2007

San Francisco International Airport (SFO) is typical of many large airports in that rapid growth in air travel has outpaced its available runway capacity, leading to serious delays. At the same time, SFO represents a unique circumstance because of the role of its local climate, and thus careful analysis is required to address its delay situation. The airport is in the process of planning a major runway reconfiguration project that would largely solve the problem of weather-related congestion delays, but this massive project will take many years. Presented are the results of an effort to design potential short-term strategies to reduce weatherrelated congestion delay at SFO while the runway reconfiguration proceeds. Designing measures to reduce delay outside the context of runway expansion is a complex task that requires balancing multiple considerations—issues of equity, access, legal jurisdiction—along with considerations of efficiency and airport performance. The kinds of thinking and analysis required in considering these types of delay-reduction measures are explored.
Computing and Interpreting Accident Rates for Vehicle Types or Driver Groups
Authors: Hauer Ezra
Published: April 2007

Two questions are addressed. The first question is, Which of the many rates that have been proposed for measuring the safety of certain vehicle types of driver groups is to be trusted? It is concluded that for a rate to be correct, the numerator and the denominator must pertain to the same entity. If vehicle exposure is in the denominator, then the count of vehicles of some type in accidents (and not of accidents involving vehicles of some type) must be in the numerator; if driver exposure is in the denominator, then the count of drivers of some kind in accidents (and not of accidents involving that kind of driver) must be in the numerator. The second question is, What meaning can be attributed to a finding of overrepresentation? It is concluded that because reported accidents of specified severity are always used, overrepresentation may be caused by a mix of three factors: the probability to be in an accident per unit of exposure, the probability of the accident to be reported, and the probability of the accident to be of the specified severity. It follows that an indication of overrepresentation cannot be taken to mean that the entity has a larger-than-normal chance to be involved in accidents nor that one should seek remedies that reduce that chance of the entity to be involved in accidents.
Geographic Information System–Based Accident Data Management for Mexican Federal Roads
Authors: Mendoza Alberto , Mayoral Emilio F. , Vicente José L. , Quintero Francisco L.
Published: April 2007

A description is given of the efforts of the Mexican Transportation Institute (IMT) to develop a geographic information system (GIS)-based data management system for accidents on federal roads in the various states of Mexico with the purpose of achieving efficiency, reliability, and automation for handling and processing of such data. A description is also given of the use of the developed system for generating some relevant results. Some conclusions are derived. Although the former is shown only for the case of the state of Oaxaca, the procedure presented has been completed for the other states of Mexico. For development of this work, the Arc View GIS was selected after evaluating its characteristics of capacity versus price, because the resulting system will be delivered to each of the Centers of the Ministry of Communications and Transports in the states of Mexico. The system is developed by integrating into Arc View a series of data for the state considered, including cartographic representation, classification and naming of roads, traffic volume and composition, and information on accidents. The information referred to in the work corresponds to 1997.
Life-Cycle Cost Comparison of Asphalt and Concrete Pavements on Low-Volume Roads; Case Study Comparisons
Authors: Embacher Rebecca A. , Snyder Mark B.
Published: April 2007

The costs of pavement construction, maintenance, and rehabilitation are primary factors considered by most local agencies in the selection of pavement type [hot-mix asphalt concrete (HMAC) or portland cement concrete (PCC)] for new construction. The optimal use of agency funds for any given project can be determined only through an economic analysis of all associated agency costs and the performance of the pavement. Life-cycle cost analyses were performed on HMAC and PCC highway pavements in Olmsted and Waseca Counties, Minnesota. The Means Heavy Construction Historical Cost Index and the Minnesota Department of Transportation Surfacing Indices were used to convert all expenditures over time into equivalent constant-dollar values. Direct comparisons were made on roadway sections with similar traffic volumes, ages, and environmental conditions. For Olmsted County, the favored pavement type depended somewhat on the cost index values that were used in the analysis; however, index selection had no effect on the outcome for the Waseca County comparisons. When the results were normalized for traffic volumes (i.e., cost per lane mile per million vehicles carried), PCC pavements were clearly more cost-effective in all Olmsted County cases and all but one Waseca County case, regardless of the cost index value used. PCC pavements generally incurred significantly lower maintenance and rehabilitation costs than HMAC roadways in both counties.
Pilot Installation of a Bridge Scour Monitoring Site
Authors: Weissmann José , Chun Huong , Haas Carl
Published: April 2007

A pilot scour monitoring system was installed at the Mustang Creek bridge crossing on FM-1157 in Jackson County, Texas. It consists of four ultrasonic sensors mounted on four bridge piers. Maintenance engineers have access to the scour and stage data remotely through a cellular phone and modem at the site, which are powered by a battery and solar panels. The datalogger at the site is capable of monitoring multiple types of sensors, such as pressure transducers for stage, and ultrasonic and magnetic sliding collar sensors for scour. This fully programmable datalogger can generate alarm calls to an office computer when certain preprogrammed thresholds for stage and scour are reached. Automatic paging software, residing in an office computer, sends alarm calls to alphanumeric pagers carried by Texas Department of Transportation maintenance staff, based on alarm callbacks from the datalogger in the field.
Reliability and Accuracy of In-Depth Inspection of Highway Bridges
Authors: Graybeal B. A. , Rolander D. D. , Phares B. M. , Moore M. E. , Washer G. A.
Published: April 2007

In-depth inspection is one of the two most common types of bridge inspection. In contrast with routine inspection, in-depth inspection is a close-up, hands-on inspection that generally covers only a portion of a bridge. The Federal Highway Administration’s Nondestructive Evaluation Validation Center recently completed a study of the reliability of visual inspection of highway bridges. Part of this study focused on the accuracy and reliability of in-depth inspections as completed by state bridge inspectors from across the United States. Three in-depth inspection tasks were completed, two focusing on the inspection of steel superstructures and one focusing on the inspection of concrete bridge decks. Visual inspection techniques were used, with the possible use of simple inspection tools. Results show that many in-depth inspections completed by state bridge inspectors do not accurately represent the condition of the structure. In-depth inspections of the steel superstructures revealed that certain deficiencies for which this type of inspection is frequently prescribed were rarely detected. Specifically, only a small minority of state bridge inspectors located the presence of any of the existing crack indications. The delamination survey of a concrete bridge deck indicated that the accuracy of this type of inspection is relatively poor. Very few state bridge inspection teams provided results that could be considered to portray the condition of the deck accurately.
Analysis of Aggregation Effects in Vehicular Emission Estimation
Authors: Zietsman Josias , Rilett Laurence R.
Published: April 2007

In the United States, most emissions modeling is done using the MOBILE suite of programs. One of the inputs required is vehicle kilometers of travel (VKT) for each vehicle class as a function of average speed. This information traditionally has been obtained from macroscopic planning models whereby the average speed on a given length of roadway is the same for all vehicle classes. During the past 10 years, however, there has been a definite shift away from macro-level transportation modeling to a more simulation-based approach. In addition to the advances in modeling techniques, the advent of intelligent transportation systems (ITS) has opened numerous possibilities for capturing detailed transportation-related information. The purpose of this paper is to illustrate the trade-offs involved under different aggregation scenarios for estimating vehicular emissions using data sets produced by microsimulation models and ITS. A 22-km section of Interstate 10 in Houston, Texas, was used as the test bed in this study. The VKT and speed data for this corridor were determined using a calibrated TRANSIMS model. This information was then used with the MOBILE5a emission model to compute emission estimates. The vehicular emissions were determined for a broad range of spatial, temporal, and combined spatial and temporal levels of disaggregation. It was found that emission estimates could vary by as much as 20 percent, depending on how the VKT and speed data are determined or depending on the type of ITS data-collection technology used.
Safety Effect of Roundabout Conversions in the United States: Empirical Bayes Observational Before-After Study
Authors: Persaud Bhagwant N. , Retting Richard A. , Garder Per E. , Lord Dominique
Published: April 2007

Modern roundabouts are designed to control traffic flow at intersections without the use of stop signs or traffic signals. U.S. experience with modern roundabouts is rather limited to date, but in recent years there has been growing interest in their potential benefits and a relatively large increase in roundabout construction. This interest has created a need for data regarding the safety effect of roundabouts. Changes in motor vehicle crashes following conversion of 23 intersections from stop sign and traffic signal control to modern roundabouts are evaluated. The settings, located in seven states, are a mix of urban, suburban, and rural environments with the urban sample consisting of both single-lane and multilane designs and the rural sample consisting of only single-lane designs. A before-after study was conducted using the empirical Bayes procedure, which accounts for regression to the mean and traffic volume changes that usually accompany conversion of intersections to roundabouts. For the 23 intersections combined, this procedure estimated highly significant reductions of 40 percent for all crash severities combined and 80 percent for all injury crashes. Reductions in the numbers of fatal and incapacitating injury crashes were estimated to be about 90 percent. In general, the results are consistent with numerous international studies and suggest that roundabout installation should be strongly promoted as an effective safety treatment for intersections. Because the empirical Bayes approach is relatively new in safety analysis, the potential of this methodology in the evaluation of safety measures is demonstrated.