Arun Chatterjee

Estimation of Traffic Volume on Rural Local Roads

Traffic volumes on local roads have not received much attention from highway planners and researchers, although local roads constitute the majority of road mileage in a state. In recent years the need for reliable estimates of vehicle-miles of travel on local roads has been recognized for the analysis of air quality and highway safety issues. To provide a better understanding of traffic volumes on local roads and to explore alternative methods for estimation, data from Georgia were analyzed by using different statistical procedures. The findings of this analysis are presented, along with the results of an attempt to develop a mathematical model for estimation of local road traffic volumes.

A specialized equilibrium assignment algorithm for air quality modeling

Abstract A multiple user class equilibrium assignment algorithm is formulated to determine vehicle trips and the vehicle miles of travel (VMT) in various operating modes on highway links. A heuristic solution algorithm based on the Frank–Wolfe decomposition of the equilibrium assignment problem is presented. The treatment of intrazonal trips, which are very important for emission studies is also discussed. The solution algorithm is implemented in a traffic assignment program for emission studies, referred to as TAPES. The use of the algorithm is demonstrated through a TAPES model case study on a Charlotte, NC network database for 1990 AM peak period. The operating mode mix of VMT in cold transient, hot transient and hot stabilized modes, also known as the mix of cold-starts, hot-starts and stabilized mode trips, is derived on a link by link basis. The results are aggregated by facility type and the location of link segments. It is observed that the operating mode fractions in transient and stabilized modes could vary widely across different facility types geographic locations. The aggregated operating mode fractions derived from the assignment analysis indicates that a lesser proportion of VMT operates in cold and hot transient modes when compared to the operating mode mix derived from the Federal Test Procedure (FTP).

NON-COMMITMENT BIAS IN PUBLIC OPINION ON TRANSIT USAGE

Estimation of ridership on a new transit system in an area where no comparable service existed before is a difficult task of transit planning. Traditional modal split models cannot be used in these cases, because no data or basis for developing a new model or adjusting a “borrowed” model are available. One of the techniques which can be used in this type of situation, is to perform a “concept test” based on public opinion. This approach, however, is plagued with the phenomenon of non-commitment bias of interviewees, and tends to overestimate the ridership.A new fixed route and fixed schedule transit service in Johnson City in Tennessee provided a rare opportunity to perform an investigation on the non-commitment bias through “before” and “after” surveys. The analysis of the non-commitment and actual responses of a sample of residents revealed substantial bias. Overall, the non-commitment ridership estimate was about twice (100% greater than) the actual ridership.:It was also observed that the bias was higher for persons owning automobiles, and for work and shopping trips.

Incorporating Safety and Security Issues in Urban Transportation Planning

The Transportation Equity Act for the 21st Century specifically mentions safety and security as making up one of the seven factors to be considered as metropolitan planning organizations (MPOs) develop their transportation plans and programs. In order to assess the current practice, visits were made to several MPOs and transit districts around the country to learn how safety and security were being addressed in both the long-range and short-range transportation planning processes. Although safety and security were reflected in planning policies and goals and short-range project selection and programming incorporated measures of safety and security, there were few instances in which long-range planning incorporated these issues. In many cases the lack of data and limited analysis tools resulted in a reliance on subjective assessments of safety and security issues. The findings from the case study-oriented project are documented.

Overnight Truck Parking Along Tennessee's Interstate Highways and Rest Areas

Truck parking spaces in the public rest areas and pull-out areas along Tennessee’s Interstate highways are filling up at night, and large trucks are parking along the shoulders of ramps to these areas. Trucks are also parking along regular interchange ramps and in some cases along through lanes. This is a potentially hazardous situation for travelers. A detailed survey was performed at public rest areas in Tennessee at night, covering all 7 days of the week, to learn about the occupancy characteristics of trucks. Availability of space in private truck stops near interchanges also was examined. This research presents the findings of these surveys in quantitative terms. Several truck drivers were interviewed and all neighboring states were contacted to learn more about why some drivers prefer to park along highways and what strategies are being used by other states to alleviate this problem. Findings related to these issues are presented in this research.

Macro-Level Analysis of Factors Related to Areawide Highway Traffic Congestion

The relationship between traffic congestion, travel demand, and supply of roadways is investigated by use of the travel rate index, a congestion measure developed by researchers at the Texas Transportation Institute. Data for the top 138 urbanized areas (by population) were assembled for developing a least-squares regression model. The travel rate index was selected as the response (dependent) variable. A variety of explanatory variables were used to address highway and transit supply and travel demand-related factors. The partial regression coefficients measured the effect of each explanatory (independent) variable on congestion (as measured by travel rate index), holding all other independent variables constant. The results of the multiple regression analysis indicated a negative correlation between freeway lane miles and combined travel rate index. Additionally, a strong positive correlation was observed between combined travel rate index and population density and net land area. A positive correlation was observed between combined travel rate index and bus transit service revenue miles. Principal arterial lane miles and rail transit revenue miles variables were not observed to be significant for explaining traffic congestion and were removed entirely during the stepwise regression. The results indicated that the best predictors among the tested variables were freeway lane miles, population density, net land area, and bus revenue miles. When used together, these predictors accounted for approximately 61% of the total variation in the dependent variable, combined travel rate index.

Effect of Increased Truck Traffic from Chickamauga Lock Closure

The lock at Chickamauga Dam on the Tennessee River may have to close for various periods for major repair work. Such scheduled or unscheduled closures will disrupt the barge traffic serving many industries located upstream of the dam. Some of the commodities moving on barges will be diverted to trucks, depending on the nature of the closures, and the new truck traffic may result in a variety of effects, or externalities. A method is presented to estimate the effects of increased truck traffic. Delays from traffic congestion and incidents, pavement damage, truck-related accidents, and air pollution are examined. The study was performed for the Tennessee Valley Authority.

LANDSIDE ACCESS TO SEAPORTS IN URBAN AREAS: A CASE STUDY

Seaports in the United States usually are located in urban areas. They are major traffic generators on the landside. However, the landside access needs of ports often are overlooked by the transportation and land-use planning processes. A case study of three ports on the East Coast of the United States was performed: Savannah, Georgia; Wilmington, North Carolina; and Morehead City, North Carolina. Both highway and rail access issues were examined at regional and local levels. Several serious issues and problems are identified and discussed in the paper, including effects on local communities.

Travel Characteristics of Urban Freight Vehicles and Their Effects on Emission Factors

This study collected local commercial vehicle data in Knox County, Tennessee, from the U.S. Postal Service (USPS) and two companies engaged in package pickup and delivery (PUD). Another urban commercial vehicle data set with a wider spectrum of freight companies was obtained from North Carolina for comparative analysis. The two data sets were analyzed to develop two sets of values for input parameters for the U.S. Environmental Protection Agencys MOBILE6 model. Statistical test permitted four aggregated vehicle usage classes to be formed. Two runs of MOBILE6 modeled the two commercial vehicle data sets in their entirety. Four additional runs modeled each vehicle usage class individually through the use of average speed and starts per day specific to the driving pattern of each class. Differences between the values of input parameters and emission factors based on data collected by this study and those based on the default values of MOBILE6 are discussed. Commercial vehicles examined by this study indicat...

Assessing safety impacts of long-range plans in small and medium-sized communities

In updating the regional transportation plan for the Eugene-Springfield area in Oregon, the Lane Council of Governments (LCOG) developed a series of six alternative plan scenarios to test the effectiveness of various strategies (transportation demand management, land use, system changes). To measure the effectiveness of scenarios performance criteria were developed. While safety was a broad issue of interest to policy makers and the public, no safety criterion was found that could be modeled and forecasted in a practical manner. In 2001, a research project was undertaken by the University of Tennessee to develop and test practical tools for assessing safety impacts of transportation plans for urban areas. As part of this research, LCOG was engaged to apply a set of accident rates to its alternative long-range plan scenarios. This study concludes that, in general, at the point where issues raised as part of this application are addressed through future research, the approach of using a standard travel-demand forecasting model and a series of crash forecasting spreadsheets could provide a practical means for assessing the safety impacts of long-range plans in small and medium-sized communities. The application effort yielded several specific observations relevant to future efforts. Key issues include lack of transferability of crash data, availability of and easy access to detailed crash data for a given urban area, refinement of continuous functions for developing crash forecasts, and refinement of intersection crash analysis methods.