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A Message from the JTRF Co-General Editors
The Fall 2006 issue contains the usual wide variety of transportation topics that distinguishes JTRF from other transportation journals. Topical areas include:
- Predicting service lives of pavement marking materials
- Transportation performance measurement
- Effect of driver attitudes on speed limit laws, seatbelt use, and drinking-and-driving
- Imputing missing traffic volume data
- Impact of summer storms on aviation system performance
- Productivity, pricing, and profitability in the rail industry
- Emerging commuting trends
In "Methodologies to Predict Service Lives of Pavement Marking Materials," Yunlong Zhang and Dongfeng Wu develop methods to predict the service lives of 95 pavement marking materials based on their retroreflectivity. The authors employed the smoothing spline method and time series modeling to estimate the service lives of different marking materials. They found that both models can predict retroreflectivity of pavement marking materials for the following six months with reasonably good accuracy. Zhang and Wu demonstrated in a Mississippi case study that the predicted service lives of pavement marking materials can be used in life-cycle cost comparisons for selecting pavement marking material.
Haiyuan Wang and Mingzhou Jin propose a set of transportation system-level performance measures in "A Transportation Performance Measurement System with a Mississippi Case Study." The authors present a set of user-oriented, scalable, and systematic performance measures. They also employ a case study to demonstrate how to collect data from existing sources, how to calculate the measures, and how to evaluate transportation system performance based on the measures. Wang and Jin develop five performance measures including mobility and reliability for travel time, safety measures, environmental impact, long term transportation cost efficiency, and economic impact. The authors note that their proposed measurement system can be applied to all modes.
In "Driver Attitudes and Choices: Speed Limits, Seat Belt Use, and Drinking-and-Driving," Young-Jun Kweon and Kara M. Kockelman examine drivers' seatbelt use, driving speed choices, and drinking-and-driving tendencies, along with their attitudes regarding speed limits and seatbelt laws. The authors employed ordered probit, negative binomial, and linear regression models to measure driver behavior. Kweon and Kockelman obtained many interesting results concerning driver attitudes. For example, males are less likely to use a seatbelt and favor seatbelt laws, but more likely to favor raised speed limits, to drive faster, and to drive after drinking.
Mei Chen, Jingxin Xia, and Rongfang Liu present a comparative analysis of various methods for imputing missing traffic volume data in "Developing a Strategy for Imputing Missing Traffic Volume Data." The alternative methods include historical average, temporal and spatial interpolation, hybrid algorithm, and artificial neural networks. Chen, Xia, and Liu found that the relative performance of the different methods varied by time-of-day and day-of-week factors, and each method had its strengths and weaknesses. The authors developed an implementation strategy for the Kentucky traffic data management system based on the performance of the various imputation methods.
In "Aviation System Performance During the Summer Convective Weather Season," Kenneth Wright analyzes recent trends related to flight delays and airborne holding and diversions during the summer season. He develops a weather metric that accounts for the location and intensity of thunderstorms. The metric can be used in regression models to help identify and explain changes in aviation system performance. Wright found that regression models that used his weather metric found substantial increases in delays lasting more than an hour from 2003 to 2005, and that the increases in delays appear to be because of a greater concentration of flights at the busiest airports. He found that regression analysis containing the weather metric and other variables found a large increase in airborne holding in the summer of 2005 compared to the previous two summers. The increase appears to be due to a doubling of holding at Atlanta according to the author.
Carl D. Martland analyzes trends in U.S. railroad productivity, pricing, and profitability in "Productivity, Pricing and Profitability in the U.S. Rail Freight Industry, 1995-2004." He provides insight into the extent and sources of productivity improvement in the U.S. rail industry since 1995, and the extent to which productivity improvement has led to improved financial performance. Martland found that from 1995 to 2004, rail productivity increased 5% per year, rail prices fell, and financial performance was flat or declining. Martland discovered that by 2004, the long term trends in the rail industry were coming to an end: the rate of productivity improvement was declining, rail rates were starting to increase, and capacity and service problems were becoming more serious. With higher rates, many of the Class I railroads were close to earning their cost of capital according to the author.
In "Emerging Commuting Trends: Evidence from the Chicago Area," Siim Sööt, Joost Gideon Berman, and Joseph DiJohn discuss changes in urban commuting patterns during the 1960-2000 period using Chicago data to illustrate the changes. They found that in the 1990s the percentage growth in the number of Chicago workers was less than the growth in Chicago population, which mitigated the major increases in congestion that were forecast in the 1980s. The authors attributed this to the fact that household size has stopped declining. In addition, employment has increased significantly in the Chicago suburbs resulting in major increases in commuting between suburbs. This inter-county commuting has contributed to longer commutes.
Kofi Obeng
Co-General Editor - JTRF
Michael W. Babcock
Co-General Editor - JTRF
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