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The Maryland Mass Transit Administration conducted an LNG transit bus demonstration in Baltimore, Maryland. A refueling facility was constructed and maintenance facilities were modified to provide support for the demonstration. During the demonstration operational data were collected on the buses and facilities. Problems encountered with the vehicle LNG fuel systems are reviewed and discussed. This paper summarizes the findings and operation of the LNG fleet during the demonstration and projects future LNG vehicle and operational costs.

The Maryland Mass Transit Administration has operated four liquefied natural gas (LNG) transit buses since late 1993. LNG is unique among alternative fuels in that it has a short “shelf life.” As a result of heat gains, LNG fuel weathers at predictable rates, resulting in the potential loss of fuel mass and the potential loss of methane content. Early experience with LNG transit buses included engine failures due to insufficient octane caused by low methane content of the fuel. LNG systems can be managed to offset the effects of fuel weathering, given consistent fuel quality. Methods of predicting LNG fuel quality after weathering has occurred (both bulk and onboard storage tanks) are presented based on field experience. Vehicle operational management techniques that can reduce LNG weathering and possible engine damage are also presented.

The Maryland Mass Transit Administration (MTA) is demonstrating the use of liquefied natural gas (LNG) as a cost-effective and low emission transit bus fuel. The potential advantages of LNG as a transit bus fuel relative to using compressed natural gas (CNG) include lower fuel system weight, smaller volume required for the fuel system components, shorter time required for refueling and lower refueling facility cost, more uniform and higher fuel quality, and less demand on utility gas line flow limits. The LNG storage and dispensing system must be engineered in conjunction with the LNG fuel system on the bus to achieve fast, reliable and safe refueling. This paper describes the LNG storage and dispensing system designed and built to support the Maryland MTA demonstration of LNG transit buses.