Technology Review has an article on fuel efficient, low pollution Dutch buses that use in-wheel motors - Wheel Motors to Drive Dutch Buses.

A company based in the Netherlands called e-Traction has developed a new kind of hybrid bus that uses in-wheel electric motors to improve efficiency and a GPS system to reduce pollution in congested areas of a city. The bus is a series hybrid: a diesel generator charges a battery, which in turn supplies electricity for two motors, one in each rear wheel. Thanks largely to its in-wheel motors, the bus can travel twice as far as a conventional bus on a liter of diesel, says Arend Heinen, who is both an engineer and spokesperson for the company. That translates into a fuel-economy improvement of 50 percent. The company has been awarded contracts to retrofit seven commercial buses with its technology, with the first to be completed next month.

In-wheel motors have been around for some time: they have been used in several concept cars and experimental, low-production vehicles. But with the exception of electric bicycles, the idea has never found its way into a mass-production vehicle, says John Boesel, the president and CEO of Calstart, a nonprofit based in Pasedena, CA. The use of e-Traction's system in commercial buses would be a step toward more widespread use.

As with other hybrid buses, thousands of which are already in use in the United States, e-Traction's design saves fuel by capturing energy from braking, using it to generate electricity that can later be employed for acceleration. The in-wheel motors confer additional savings by eliminating the need for a transmission, differential, and related mechanical parts. That reduces both the overall weight of the bus and energy losses due to friction. Hybrid buses typically see fuel-economy improvements of about 25 to 30 percent compared with conventional buses, but e-Traction's design offers 50 percent improvement. In certain conditions--at low speeds in frequent stop-and-go traffic--some other hybrid buses have seen similar fuel-economy improvements. The in-wheel motors can also improve traction by allowing precise control over each wheel, and they allow for greater flexibility in vehicle design since there is no need to mechanically link the wheels to an engine.

The bus also incorporates a GPS-based system that changes the way that the bus operates in congested areas. In ordinary operation, the generator cycles on and off, keeping the battery at an optimal state of charge. But when the GPS system senses that the bus has entered an area of the city that usually sees a lot of traffic, the generator switches off to reduce emissions. The battery stores enough power to propel the bus for an hour without the generator running to recharge it.

PhysOrg has an article on a new, more efficient hybrid bus made using a lightweight nitrogen-strengthened stainless steel - Revolutionary green technology bus.

Insight from Oak Ridge National Laboratory, commitment from two Michigan companies and funding from the Department of Energy have led to the commercialization of a lightweight urban transit bus with double the fuel efficiency of conventional hybrid buses.

This new green technology 40-foot bus features a high-strength stainless steel body and chassis and a hybrid power system that drives the bus primarily with stored electrical energy. This approach reverses the paradigm of conventional parallel hybrid designs that use electric energy only to supplement the acceleration and torque requirements of a diesel engine.

At the heart of the bus is a chassis made of Nitronic 30, a nitrogen-strengthened stainless steel that is stronger and stiffer than conventional steel. These attributes translate into less material required for a chassis, resulting in reduced weight.

"Nitronic stainless steel is incredibly durable and enables our chassis designs to have significantly longer service life vs. ordinary steel vehicles," said Bruce Emmons, president of Autokinetics (http://www.autokinetics.com/) of Rochester, Mich., which developed the bus. "The fact that stainless is also 100 percent recyclable and more environmentally friendly to produce than aluminum makes this an ideal green raw material for vehicle structures."

The Washington Post reports that the US state of Maryland is to convert its bus fleet to hybrids.

Gov. Martin O'Malley wants Maryland's entire fleet of transit buses to be diesel-electric hybrids. O'Malley announced Tuesday that he has directed the Maryland Transit Administration to purchase only hybrid buses in the future as older buses powered only by diesel fuel are taken out of service.

The state says hybrid buses use up to 20 percent less fuel and are up to 40 percent quieter. They're also more reliable, going 6,200 miles between service calls, compared with 3,000 miles for diesel models.

There are currently 653 buses in the MTA fleet, and 10 are hybrids. MTA spokeswoman Jauwana Greene says the agency has been given approval to buy up to 100 hybrids a year starting next year. She says if buses are replaced at the usual rate, there should be about 500 hybrids in the fleet by 2014.