They’ll run on regular routes for a year to see how they perform in the city’s climate and road conditions. “Reliability, performance, maintenance costs, fuel efficiency, noise generation, and environmental impact will all be monitored and evaluated to determine which model, if any, might become part of the regular fleet in the future,” explains Jim Bryant, Bus Fleet and Equipment Maintenance Supervisor for Edmonton Transit.

Hybrids use a combination of diesel and electrical power for propulsion. They are more energy efficient and environmentally friendly than regular diesel buses, Bryant says. “There is good evidence to suggest that fuel savings may be as much as 20 to 25 per cent over conventional diesel buses.”

However, ETS wants to ascertain whether their lifecycle cost is actually less, because the hybrid models sell for about $250,000 more than a conventional $400,000 diesel bus. “Each vehicle also requires a roof-mounted battery pack which has to be replaced every six to eight years.” Bryant explains. “At the end of the test period we’ll determine whether those extra expenses will be fully offset by the savings in fuel and maintenance costs.”

The experience in other cities shows that diesel/electric hybrids do indeed have some advantages. They cost less to operate, get better fuel economy and pollute less than their diesel counterparts.

But they still pollute more than electric-drive trolley buses, and Edmonton is one of only two cities in the country that has retained its electric trolley fleet. Now, with the price of fuel going up and with more concerns about air pollution right where we live, trolleys are looking like the best approach, even including the new hybrid technologies.

According to General Motors, if America’s nine largest cities were to replace their existing fleets of a combined 13,000 transit buses with hybrid buses, the United States would save about 160 million litres of fuel a year. No wonder the technology is catching on in a big way, especially south of the border.

In New York City, 825 Orion hybrid buses are in service or on order; King County Metro, which serves Seattle, has 235 now in service; this summer, San Francisco added 56 Orion hybrids to its fleet; and Toronto has 150 on order. BC Transit runs three GM-Allison diesel hybrids in Victoria and three in Kelowna.

The low-floor Orion VII hybrid bus, manufactured by Daimler Chrysler’s Commercial Bus division, uses a HybriDrive propulsion system provided by BAE Systems Platform Solutions. The system propels the bus with a single electric motor that is powered by a diesel-driven generator and an energy storage unit.

The engine is smaller than that used in conventional buses and it runs at optimum speed for clean operation and efficiency. The system combines a 5.9-liter, 260 hp (194 kW) Cummins ULSD (Ultra Low Sulphur Diesel) engine with a 120 kW traction generator. The electric traction motor delivers 250 hp (186 kW) and 2,700 lb-ft (3,657 Nm) of low-end torque.

The electric engine keeps the noise down, resulting in a quieter ride. The substantial torque of the system provides acceleration that is more brisk than a conventional diesel, helping bus drivers merge more efficiently into traffic.

The design eliminates the transmission, removing a major maintenance item on vehicles operated in heavy stop-and-go conditions. A regenerative braking system reduces brake way by about one third, reducing the frequency of brake maintenance. It uses the drive motor to slow the bus, turning the motor into a generator that recharges the energy storage system. effectively turning the motor into a generator to help recharge the energy storage system.

A study by the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) found that the Orions in service in New York City—the largest fleet—achieve up to 45 per cent better fuel economy compared to conventional diesel buses. The technology also reduces emissions considerably, with 90 per cent reductions in particulate matter, 40 per cent fewer nitrogen oxides (Nox) and 30 per cent fewer greenhouse gases.

Edmonton Transit will also be testing four New Flyer diesel/electric hybrids – the DE40LF with GM/Allison Parallel Hybrid Drive and the DE40LF with ISE Thundervolt Drive. New Flyer hybrids have been on the road for nine years, the longest of any manufacturer in the US and Canada, and have accumulated more than 12 million service miles.

By routing many of the peripheral systems like heating and air conditioning through the electrical system, this hybrid system dedicates more engine power to moving the bus, and that further increases performance.

Testing by NREL of the GM/Allison hybrid fleet used by King County Metro indicate that the hybrids deliver decreased fuel consumption of 20 per cent to 43 per cent, depending on where they are run. They also generate 10 per cent to 39 per cent fewer NOx emissions and a 51 to 97 per cent reduction in particulate matter emissions.

King County Metro requested that their buses be up-powered with Caterpillar C9 8.8-litre diesel engines. The hybrids tested are 60-foot articulated buses equipped with a GM/Allison system that is a precursor to a hybrid system now under development by GM, DaimlerChrysler and BMW.

It’s all a hybrid of some new ways of thinking about motive power.