Vehicle types
In 1978, Metro was the first large transit agency to order high-capacity articulated buses (buses with a rotating joint). [9] Today, King County Metro has one of the largest articulated fleets in North America (second only to MTA New York City Transit) and articulated buses account for about 42% of the agency's fleet. [10]
In 1979, the agency ordered some of the first wheelchair lift equipped coaches in the nation, [11] [12] promising a completely new level of independence for disabled residents. Early lifts were severely flawed, but by the mid-1980s the lifts were generally reliable and were ordered on all new buses. Metro's entire fleet has been wheelchair-accessible since 1999.
Metro was reluctant to adopt low-floor buses, not buying any until 2003. Low-floor coaches have slightly reduced seating capacity (because the wheelwells intrude further into the passenger compartment) which may have been a concern. Whatever the reason for the delay, Metro has now embraced low-floor buses and all new fleet additions since 2003 have been low-floor and the last high-floor buses were retired in March 2020.
Trolleys
Metro maintains a fleet of electric trolleybuses that serve 15 routes along almost 70 miles [13] of two-direction overhead wire. This is the second largest trolleybus system in the United States by ridership [14] and fleet size. [15] The trolleybuses are valued by Metro both as zero-emission vehicles, [16] and as vehicles well adapted to Seattle's hilly terrain.
Metro's trolleybus fleet consists of 174 entirely low-floor New Flyer Xcelsior coaches. [17] Of the total, 110 are 40-foot (12 m) vehicles (model XT40) and 64 are 60-foot (18 m), articulated buses (model XT60). [17] The buses include an auxiliary power unit, to allow them to operate off-wire for up to 3 miles (4.8 km).
Occasionally Metro will use diesel or diesel-electric hybrid coaches on trolley routes. Reasons for doing this include construction (weekends only), [18] overhead wire maintenance or events that require coaches to go long distances off-route, "coach changes" (replacing a bus in service that has developed a problem) or to add temporary additional capacity. The latter two cases sometimes lead to diesel buses being used, in order to get the replacement or supplementary vehicle into service as quickly as possible; diesel buses can reach the point of entry into service faster, as they do not need to follow the overhead wires when deadheading.
Diesel-electric hybrids
Metro operates the largest fleet of hybrid buses in the country. The first hybrid buses were purchased in 2004 for use with routes that operated in the Downtown Seattle Transit Tunnel. [19] The National Renewable Energy Laboratory conducted a one-year comparative study between conventional diesel and hybrid-powered buses operating on a typical King County drive cycle. Results showed that the hybrid powered buses lowered fuel consumption by 23%; NOx by 18%; carbon monoxide (CO) by 60%; and total hydrocarbon (THC) by 56% when compared to conventional diesel buses. Those results have led Metro to purchase hybrid buses exclusively since 2005 (with the exception of the all-electric trolley buses). [20] [21] Metro now has over 700 hybrid buses in the fleet, with more on order.
Hush mode
Buses equipped with the GM-Allison EP50 and the Allison H 50 EP parallel hybrid systems had a special "hush mode" that allowed the buses to operate solely on electric power, reducing tailpipe emissions and noise while operating in the Downtown Seattle Transit Tunnel. [19] Before entering the tunnel, the operator pushed a button that put the coach into hush mode. While buses were inside stations, the coaches operated solely on electric propulsion (although, while the doors are closed, the engine still rotates in order to operate auxiliary loads). In between the tunnel's stations, the buses used electric traction to get to 15 mph (24 km/h), after which a combination of the electric and diesel motors were used. The operation of the diesel engine allowed the batteries to recharge. Hush mode would normally be deactivated by the operator as they exited the tunnel, but the mode will be automatically deactivated after the coach had traveled a certain distance.
Buses have not operated in the tunnel since March 23, 2019. [22]
Series hybrids
Metro's newest buses are equipped with the BAE Systems HybriDrive, a series hybrid system. [23] In these buses an electric motor turns the wheels, with power provided by a generator attached to a diesel engine and regenerative braking. Any excess power is stored in batteries on the roof of the bus. Because the diesel engine is not directly propelling the bus, it can operate at a more steady, fuel-efficient speed.
Buses delivered after 2014 are equipped with the upgraded HybriDrive Series-E which uses electrically powered accessory systems (alternator, air conditioning, air compressor, cooling fans and steering pump) to increase fuel efficiency and allow the diesel engine to stop when the bus is stopped and the batteries are sufficiently charged.
Battery electric buses
Metro began testing three new Proterra Catalyst battery electric buses in 2015. [24] The coaches are capable of traveling over 26 miles [25] before the battery needs to be recharged. A special fast charge station located at the Eastgate Park and Ride allow the bus to be fully recharged in under 10 minutes, during the driver's normally scheduled layover. [26] [ non-primary source needed ] These new vehicles get the equivalent of 20.8 MPG, which is over 6 times better than the 3.18 MPG seen on Metro's series hybrid electric coaches. [27] [28] The coaches were purchased with support from a $4.7 million Federal Transit Administration grant and entered revenue service on February 17, 2016. [29] They operate on shorter routes (due to their limited range) on the eastside, specifically Routes 226 and 241. [27] [30] Metro has committed to purchasing 120 electric buses with the option to purchase up to 80 additional vehicles by 2020. In 2017 and 2018, Metro tested electric buses with ranges of 140 miles from several manufacturers, [31] and plans to have a zero-emissions bus fleet by 2040.
