In 1994, the Yosemite National Park Electric and Alternative-Fuel Shuttle Bus Demonstration Program was launched. The intent was to provide the in-valley shuttle system with a source of funding for the acquisition and testing of various alternative-fuel buses for operation on the 8.5-mile shuttle loop. Several factors contributed to the selection of the park as a test site for an electric-powered shuttle bus system. Among these factors were desires to protect the beauty of the park, reduce both exhaust and noise pollutions and test technology that could lead to advanced transportation applications in the National Park System. Four buses were acquired under this program. The buses included a 31-foot electric bus manufactured by Specialty Vehicles, a 35-foot electric bus manufactured by APS Systems and two 32-foot, 9-inch electric buses manufactured by Blue Bird Corp. Because maintenance, operation and durability features inherent to these electric vehicles proved to be extremely problematic and ineffective, none of the electric buses continue to operate on the Yosemite Valley shuttle loop.
In accordance with the Yosemite Valley Plan, the park began in 1999 to determine the general feasibility of other alternative-fuel buses for in-valley shuttle bus service. A comprehensive technology assessment was conducted covering a broad spectrum of available and emerging technologies. This assessment included extensive surveys of existing bus systems. Alternatives scrutinized included clean diesel, diesel electric hybrid, compressed natural gas (CNG), liquefied natural gas (LNG), alcohol fuels (ethanol/methanol), liquefied petroleum gas (LPG/ propane), pure battery electric and fuel cell. Evaluation criteria included commercial technology availability, performance requirements/needs, cost, fuel availability/integration, maintenance facility modifications, maintainability, technological maturity and existing/previous operator experiences. Focus groups were conducted within the park to educate and inform stakeholders of implications and opportunities presented with various technologies and systems. Operations and maintenance issues, as well as associated costs, were documented and communicated. Hybrid vehicle demonstrations have also been conducted within the park, traversing actual conditions with excellent results. . . .
In terms of propulsion technology “fit,” CNG and LNG introduce challenges to existing park infrastructures (such as the needs to construct costly fueling facilities and completely rebuild the existing 14,500-square-foot bus maintenance facility to address safety issues). Moreover, CNG and LNG only present minor, if any, emissions benefits relative to diesel hybrid, according to recent tests performed by the California Air Resources Board. Alcohol-based fuels have commercial availability limitations. Meanwhile, the park has compiled a large body of marginal performance operating experience with pure battery electric technology, which has not advanced appreciably over the past decade. In addition, several park infrastructure issues are introduced, such as the need to reconstruct the existing bus maintenance facility from a safety and efficiency standpoint, as well as install new and costly electrical infrastructure systems to facilitate recharging operations.
