Kelly BlumeMarais LombardShaun QuaylePhill Worth...
p.1-10页
查看更多>>摘要：The purpose of the Highway Performance Monitoring System of the Rural and Local Roads Reporting Project was to develop a more accurate, yet cost-effective, methodology for estimating vehicle miles traveled (VMT) on urban local roads, rural local roads, and rural minor collectors throughout Florida. A review of Florida's existing methodology, methodologies of five "peer" states, and available research was completed to develop specific evaluation criteria that could then be applied to several conceptual methodologies developed from the synthesis of information. The project team selected a preferred VMT estimation methodology that used census data and random sampling. The preferred methodology makes use of available census data and an intuitive correlation between travel and population density, job density, and roadway density, while it eliminates the dependence on volume groups that is part of FHWA's methodology for higher-order roadways. The density factors are used to group similar zip code tabulation areas (ZCTAs) into subregions to allow random samples taken in one subregion to represent similar ZCTAs statewide on the basis of any or all the following: population, job, and roadway density. A minimum number of random samples is selected to retain statistical validity while minimizing costs to conduct traffic counts. The methodology is flexible enough to allow adjustments (e.g., restratincation based on indicators such as coefficients of variation) that improve the quality of the results from year to year. Implementing a test case of the methodology to determine real-world applicability is the next logical step in the research process.
查看更多>>摘要：This paper describes the spatial information system infrastructure implemented by the Illinois Department of Transportation (IDOT) to enable delivery of information to management decision makers in asset management applications. This spatial data warehouse infrastructure makes extensive use of geographic information system (GIS) technologies to integrate information from a variety of database structures and formats. GIS products and tools have been developed to portray and analyze these data in useful combinations focused on practitioner needs. In June 1999 the Governmental Accounting Standards Board issued Statement 34 requiring governments to have a systematic approach to managing their assets. As a result, transportation agencies have placed an increased emphasis on developing mechanisms to integrate information from disparate management information systems and legacy databases. IDOT has used GIS to develop a spatial data warehouse to enable integration. A valuable characteristic of the department's information systems infrastructure is the embedding of the underlying link-node structure into roadway inventory databases to enable the direct linkage of data through various system identifiers, including differing milepost referencing and project numbering schemes. This direct linkage enables the complex integration of asset management-related data files across the enterprise and provides access to historical asset information. Changes to route referencing systems are readily accommodated, without loss of integrative capabilities. Outputs include a variety of user-developed analyses and output products with accessibility through networks, intranets, and the Internet.
查看更多>>摘要：Historically, stopped delay was used to characterize the operation of intersection movements because it was relatively easy to measure. During the past decade, the traffic engineering community has moved away from using stopped delay and now uses control delay. That measurement is more precise but quite difficult to extract from large data sets if strict definitions are used to derive the data. This paper evaluates two procedures for estimating control delay. The first is based on a historical approximation that control delay is 30% larger than stopped delay. The second is new and based on segment delay. The procedures are applied to a diverse data set collected in Phoenix, Arizona, and compared with control delay calculated by using the formal definition. The new approximation was observed to be better than the historical stopped delay procedure; it provided an accurate prediction of control delay. Because it is an approximation, this methodology would be most appropriately applied to large data sets collected from travel time studies for ranking and prioritizing intersections for further analysis.
Jacorien A. A. WoutersKin-Fai ChanJoost KolkmanRutger W. Kock...
p.28-36页
查看更多>>摘要：One objective of the Department of Transport (DoT) in the Netherlands is to provide better information to road users about the traffic situation on Dutch freeways. The idea was put forward to use existing historical freeway inductive loop data to predict a customized pretrip travel time for road users. To investigate the feasibility and usefulness of that idea, DoT launched the AIDA project. A prototype database was constructed; it contained almost 2 years of travel time data for all Dutch freeway road sections with inductive loops. A statistical algorithm was designed to compute the average travel time for any freeway journey on any future date and time. An Internet trial application was built to test the database and algorithm. Accuracy of the travel time predictions was evaluated with independent loop data. The usefulness for road users was investigated with an online survey. Results show a good match between the predicted and actual travel times. Only in 10% of analyzed cases did the actual travel time exceed the predicted travel time by more than 5 min. Of 161 respondents, 50% indicated that they found the information useful. Furthermore, 22% indicated that they would consider a different departure time on the basis of AIDA information. Thus the project has shown convincingly that the AIDA concept is not only feasible but also useful to road users. Presently DoT is looking into the uses of the concept for road users and possibly also for traffic operators.
查看更多>>摘要：Using probe vehicles rather than other detection technologies has great value, especially when travel time information is sought in a transportation network. Even though probes enable direct measurement of travel times across links, the quality or reliability of a system state estimate based on such measurements depends heavily on the number of probe observations across time and space. Clearly, it is important to know what level of travel time reliability can be achieved from a given number of probes. It is equally important to find ways (other than increasing the sample size of probes) of improving the reliability in the travel time estimate. This paper provides two new perspectives on those topics. First, the probe estimation problem is formulated in the context of estimating travel times. Second, a method is introduced to create a virtual network by inserting dummy nodes in the midpoints of links to enhance the ability to estimate travel times further in a way that is more consistent with the processing that vehicles receive. Numerical experiments are presented to illustrate the value of those ideas.
查看更多>>摘要：During the past several decades significant changes in travel behavior in the United States have occurred. Evidence from the Nationwide Personal Transportation Survey series and the 2001 National Household Travel Survey (NHTS) indicates that the average daily travel time per person has increased by 1.9 min per year between 1983 and 2001. The objective of this paper is to explore the growth of daily travel time expenditures. Changes in society, technology, incomes, attitudes, and sociodemographic and household structure have been hypothesized as having contributed to the travel time growth. This analysis explores those variables and their relationship to increases in travel time. Aggregate values are used to investigate the relationships between daily travel time expenditures and sociodemographic characteristics. This paper comments on the share of travel time growth that can be explained by the available variables and speculates on the implications of other factors on travel time expenditure growth. A review of the NHTS data set and an analysis of the relationships between the data set and travel time expenditures make clear that travel budget changes that appear to be related to the set of available variables do not explain the full reason for the significant increase in travel time spending. The increases are across all market segments: age, income, gender, ethnicity, household composition, and so on. Thus, shifts in demographic or other traveler conditions do not fully explain the increases in trip making. That has a significant implication for transportation planning-traditional sociodemographic predictors for trip making do not appear to be sufficiently causal to be useful for understanding current and future factors influencing trip making and travel expenditure changes.
查看更多>>摘要：Generally, the day-to-day variability of route travel times on, for example, freeway corridors is considered closely related to the reliability of a road network. The more that travel times on route r are dispersed in a particular time-of-day (TOD) and day-of-week (DOW) period, the more unreliable travel times on route r are conceived to be. In the literature, many different aspects of the day-to-day travel time distribution have been proposed as indicators of reliability. Mean and variance do not provide much insight because those metrics tend to obscure important aspects of the distribution under specific circumstances. It is argued that both skew and width of this distribution are relevant indicators for unreliability; therefore, two reliability metrics are proposed. These metrics are based on three characteristic percentiles: the 10th, 50th, and 90th percentile for a given route and TOD-DOW period. High values of either metric indicate high travel time unreliability. However, the weight of each metric on travel time reliability may be application- or context-specific. The practical value of these particular metrics is that they can be used to construct so-called reliability maps, which not only visualize the unreliability of travel times for a given DOW-TOD period but also help identify DOW-TOD periods in which congestion will likely set in (or dissolve). That means identification of the uncertainty of start, end, and, hence, length of morning and afternoon peak hours. Combined with a long-term travel time prediction model, the metrics can be used to predict travel time (un)reliability. Finally, the metrics may be used in discrete choice models as explanatory variables for driver uncertainty.
查看更多>>摘要：Improvements in vehicular tracking with Global Positioning Systems (GPSs) have fostered new analysis methods in transportation planning. Emerging geographical information systems have helped in developing new techniques in the collection and analysis of data specifically for travel demand forecasting. In 2002, more than 150 households in Laredo, Texas, participated in a GPS-enhanced household travel survey. Trip diary data were collected by means of a computer-assisted telephone interview (CATI), and GPS trip data were collected from survey participants' vehicles. For trip purpose, a comparison of the two data sets yielded significant results. It was found that the number of trips in the GPS data was much greater than the number reported in the CATI data. Despite that, almost all home-based work (HBW) trips found in the GPS data were also found in the CATI data. That result differs sharply from the other trip purposes: home-based nonwork (HBNW) and non-home-based (NHB); for these two trip purposes, less than half the trips found in the GPS data were found in the CATI data. That result indicates the potential for serious deficiencies in the CATI process for collecting certain types of trips in the region of study. In additional, household size and household income were found to be significant factors affecting the reporting accuracy in the CATI data. Despite that, the CATI method of household trip data retrieval is still considered to be an effective and valuable tool.
查看更多>>摘要：This paper defines a reality-based approach to soliciting stated preference data. It is related to existing preference methods in regard to both a common conceptual framework and recent trends in the literature. The reality-based approach is compared with the standard approach in both general characteristics and design procedures. Its expectations-based validity is illustrated with an application to pedestrian street-crossing behavior in the Tampa Bay area of Florida. The approach combines the realism of revealed-preference surveys and the flexibility of standard stated preference surveys. It adds to the toolbox of travel behavior research.
查看更多>>摘要：Data from large-scale travel survey databases, such as the Nationwide Personal Transportation Survey (NPTS) and the National Household Travel Survey (NHTS), are often used to derive complex parameters for transportation modeling applications not originally targeted by the surveys. When situations demand complex data manipulation tasks, publicly available tools for the purpose do not obviate the need for data users to sift through entire databases and develop custom solutions. This paper presents a flexible methodology for developing custom database tools for cost-effectively deriving application-specific information from travel survey data. The seven-step methodology accounts for assessment of needs, verification of validity of travel survey data to the application, establishment of scientific justification, development of functional requirements of the system, development of data model, definition of processes, and development and testing of tools. To demonstrate the methodology, a case study involving derivation of locality-specific parameters for emission factor models from the NPTS and NHTS databases is presented. With the use of this methodology, a custom database application called Travel-Related Inputs Model for MOBILE6.x (TRIMM) was developed for this case study. The working mechanisms of TRIMM are illustrated. The methodology outlined, though specific to travel survey databases, is sufficiently generic to be used for developing custom tools to derive various modeling parameters from large transportation databases.
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