Analysis of Trends in Commuter Rail Energy Efficiency
Commuter rail systems are widely regarded as an effective transportation alternative to reduce energy consumption and emissions in large urban areas. Use of commuter rail systems in the United States is on the rise, with annual ridership increasing by 28 percent between 1997 and 2007 [1]. With growing concerns about the sustainability and environmental impacts of transportation, modal energy efficiency is increasingly considered amongst the metrics to evaluate the benefits and costs of transportation systems and justify future investment. To gauge the relative long-term efficiency trends for rail as an urban transportation mode, this study analyzes historic trends in energy efficiency metrics for US commuter rail systems. Commuter rail systems receiving, or benefiting from, Federal Transit Administration (FTA) grants are required to report operations and energy consumption data on an annual basis to the National Transit Database (NTD). NTD data on energy consumption, operations, and services supplied from 1997 to 2011 are analyzed to determine historic trends in various energy efficiency metrics for the commuter rail mode as a whole. The data analysis and comparison of the results with the highway mode is complicated by the use of electric traction by some commuter rail operators. These operators report energy consumption in purchased electricity (kWh) instead of gallons of liquid fuel. The different approaches that can be employed to compare these two forms of propulsion and their intrinsic efficiencies and energy sources are discussed. Energy efficiency of each commuter rail system and its relationship to individual system characteristics during the study period are also analyzed. Finally, case studies of historic energy efficiency of individual commuter rail systems with longer operating histories and reporting data over the majority of the study period are contrasted against more recent start-up systems. While many systems outperform the energy efficiency of a typical light-duty vehicle, there are others that, due to a variety of system parameters and characteristics, fail to achieve a load factor great enough to make them more attractive than the highway mode on a gross average level. It is hoped that highlighting trends and variation in commuter rail energy efficiency will allow policymakers to make more informed decisions regarding the environmental benefits of rail as an urban transportation mode.Copyright © 2014 by ASME
Impact of Rising Fuel Prices on U.S. Transit Ridership
As gasoline prices have risen to unprecedented levels over the past 2 years, many transit agencies have claimed that higher fuel prices have driven ridership growth. It is determined first whether such a correlation is substantiated by the available data and then, if such correlation exists, the nature of this relationship. Five U.S. cities were selected for analysis on the basis of their level of automobile orientation and the extent and variety of transit services: Atlanta, Georgia; Dallas, Texas; Los Angeles, California; San Francisco, California; and Washington, D.C. Most of the transit systems in the five cities analyzed have experienced ridership growth since early 2004. Exceptions include the Atlanta bus and heavy rail systems and the San Francisco bus systems. With the use of time series analysis, seasonal indices, and correlation coefficients, ridership trends are evaluated and compared with corresponding national fuel prices. With the exceptions of the modes cited above and the Virginia Railway Express commuter rail in Washington, D.C., the correlation between ridership and fuel prices is statistically significant for all systems. This finding indicates that fuel price increases have indeed played a role in encouraging transit use in historically automobile-oriented American cities. Finally, the empirical relationships between fuel price and transit demand are explored. Results indicate that, on average, as fuel price increases by 1%, transit demand increases on the order of 0.24%; in other words, ridership increases approximately 0.09% for each $0.01 increase in fuel price.
Comparison of Emissions from Light Rail Transit and Bus Rapid Transit
Bus rapid transit (BRT) is an evolving and promising transit mode that has emerged as a low-cost competitor to light rail transit (LRT) in providing medium-capacity semirapid transit. In addition, recent advances in diesel and compressed natural gas technology have caused the truism “electric rail is cleaner than diesel bus” to be revisited. A partial fuel cycle comparison of the regional or urban emissions of carbon monoxide, oxides of nitrogen, and volatile organic compounds from BRT and LRT is presented. The BRT analysis includes tailpipe exhaust emissions and fuel transportation, storage, and distribution emissions. The LRT analysis contains electric power plant emissions and line-loss-induced emissions. The analysis shows that whenever equal levels of technology are compared, LRT consistently performs better than BRT despite recent advances in the BRT mode. The analysis also shows that both modes are cleaner now than in the past.