The National Park Service is embarking on a bold program to procure up to 14 clean-fuel transit buses for use as shuttles within Yosemite National Park.
Yosemite has a long history of successful transit service. Shuttle systems have been operated in the park since the late 1960s. At that time, officials saw a need for a shuttle system that would improve access to parts of Yosemite Valley with traffic congestion.
In 1980, a Yosemite master plan was instituted to ban private vehicles from parts of Yosemite Valley. Private vehicle travel to portions of the park was replaced by a free 8.5-mile shuttle system.
Since 1983, the shuttle buses in the park have been 40-foot Gillig diesel-powered transit buses. Due to age and wear, the buses purchased in 1983 were replaced in 2001 with a newer (1988 model year) lease fleet of 12 40-foot Gillig diesel-powered transit buses.
These newer buses operate to this day along the in-valley shuttle loop in anticipation of fleet replacement. The buses provide free shuttle service to up to 3 million visitors per year. The buses are designed to transport 47 seated passengers and 22 standing. Each bus annually operates approximately 15,000 miles and consumes about 4,000 gallons of diesel fuel.
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.
Park fits test parameters
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.
Assessed technologies 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.
One of the critical concerns of the park has been air quality. Tests conducted over the past several years have shown that air purity levels on a summer day in Yosemite Valley can reach levels of air pollution similar to that found in an urban environment. As documented by the park, particulate emissions generated by the current fleet of in-valley shuttle buses are a major public concern and source of comment.
Can’t hear the birds?
Acoustic noise generation has also been of paramount concern. The noise from accelerating and decelerating diesel engines reverberates off the rock walls of Yosemite Valley. Often, this reverberation is by far the loudest noise to be heard by a person standing outdoors at a number of Yosemite Valley locations. In particular, excessive bus vehicle acoustic emissions have been shown to directly impact the overall quality of visitor experience. Attempts to muffle this noise have been largely unsuccessful.
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.
Hybrids the best fit?
Diesel hybrid electric technology can offer several positive benefits and opportunities to the park. Those include the unique opportunity to enhance public image through providing a proactive, transportation-based environmental leadership position based upon responsible stewardship. This is directly demonstrated through tangible reductions in both tailpipe and acoustic emissions.
In late 2002, as part of pre-solicitation planning to evaluate diesel-electric hybrid applicability, National Park Service representatives conducted two tours of West Coast diesel hybrid electric vehicle operators. The objective was to gather and analyze real-world operator experience to ultimately assist in selecting the most appropriate technology possible.
A comprehensive risk analysis was completed to assist National Park Service in identifying risks and creating a framework for managing risks associated with the procurement and integration of diesel hybrid electric bus technology for Yosemite. This analysis has sorted through numerous risk events, identified the risks and their interrelationships and identified cost-effective ways to reduce those risks.
All identified risks were found to be reduceable to a satisfactory level or mitigated through management and planning. A combination of contractual requirements, detailed mitigation plans and thorough project oversight will lessen or prevent any of the identified risks, resulting in a successful implementation and a subsequently reliable fleet of vehicles.