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721913-1 Report Abstract

Impact of Compressed Natural Gas Fueled Buses on Street Pavements

Dingyi Yang and Robert Harrison, University of Texas at Austin, July 1995, 156 pp. (721913-1)

Federal Clean Air Act Amendments of 1990 (CAAA) and the Energy Policy Act of 1992 (EPACT), together with other state regulations have encouraged or mandated transit systems to use alternative fuels to power bus fleets. Among such fuels, compressed natural gas (CNG) is attractive, although it must be stored in robust, heavy pressurized cylinders, capable of withstanding pressures of up to 5,000 psi. Such systems are typically heavier than conventional diesel storage tanks. As a result, this raises gross vehicle weight, sometimes significantly, which then increases the consumption of the pavement over which CNG buses operate.

Capital Metro, the Austin, Texas transit authority, is currently evaluating a number of CNG fueled buses. As part of the U.S. DOT Region Six University Transportation Centers Program (UTCP), a study was instigated into the scale of incremental pavement consumption associated with the operation of these buses. The study suggests that replacing current vehicles with CNG powered models utilizing aluminum storage tanks would raise average network equivalent single rehabilitation costs across the network of over four percent. Finally, it recommends that full cost study be undertaken with evaluation of the adoption of alternative bus fuels – which includes pavement and environmental impacts.

Keywords: Transit, Pavement Costs, Full System Costs

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Reference Report #721913-1