by Jenny Minard
BBC Berkshire Reporter
Hybrid buses are powered by a mix of an ordinary diesel engine and an electric motor
Reading now has something in common with cosmopolitan cities such as New York and San Francisco - hybrid buses.
The first six Reading-routed eco-friendly buses hit the roads next week with the rest of the fleet to be in service by 2012.
The double deckers cost £300,000, but the government has paid £108,000 towards fitting the hybrid system.
BBC Berkshire has found out how they work and whether they will actually have an effect.
The new buses use a technology that was perfected by BAE Systems for the North American market, where there are more than 2,000 hybrid buses in such cities as Toronto and Houston.
"BAE Systems claim there will be a 40% fuel saving," James Freeman, chief executive officer from Reading Transport Ltd said.
"When the demonstrator bus ran in Reading for a couple of days it accomplished 7.7 mpg - compared to about 5.5 of a typical diesel double-decker in our fleet.
"There are only six buses in the first batch, so the fuel savings in absolute terms for these is expected to be about £150,000 in the first year."
Brian Robinson, a safety and sustainability specialist at Transport Research Laboratory, explained how the buses work.
"It's an electric motor that drives the wheels and makes the vehicle move, but there is a diesel engine which is acting as a generator to generate the electricity.
"This charges the battery which is used to power the motors.
"It allows the diesel engine to operate at maximum efficiency. It doesn't need to power the wheels directly, it doesn't need to drive a gear box, it doesn't need to speed up or slow down and so it can just run at a steady speed.
"As we all know from driving a car, you get the best fuel efficiency if you stay in one gear and at a steady speed.
"Because the diesel engine is not directly linked to the vehicle's wheels it will just run at a steady speed and electric motors are more efficient at stopping and starting. They don't lose so much energy.
"A crucial part of the system is the regenerative braking. The energy which is lost as the vehicle slows down - which of course buses do a lot at bus stops - is actually captured by the electric motor that runs backwards under braking and pumps energy back into the battery."
He explained that the new system will make a difference both to emissions and the fuel bills for the bus operator.
"In the grandest scheme of things, buses don't consume a huge amount of fuel compared to cars and trucks.
"But if you're a bus operator, a big part of your operational budget is the money you spend on fuel.
"If you can get a bus that carries the same people over the same route that uses 30% less fuel as these tend to do, then that's a 30% saving in fuel bill as well as a 30% saving in emissions."
A bio-ethanol scheme was introduced in Reading in 2007 but they ended up costing £350,000 more than the regular buses.
"The bio-ethanol experiment was about reducing emissions, particularly carbon dioxide," James Freeman said.
"It was never expected to save fuel because bio-ethanol fuel is by its nature less efficient than diesel. It was hoped that the price per litre would be lower than for diesel, but it wasn't.
"Furthermore the government decided to tax bio-ethanol as a road fuel rather than any sort of exceptional fuel.
"The extra cost was because the buses had a miles per gallon consumption of about 3.5, compared to a diesel bus of similar configuration at about 5.5 mpg."
As well as Reading Transport Ltd noticing a difference in their fuel bill, it is the passengers using the new buses who will also see a difference in their journeys.
"Take-up is much smoother. With no gearbox there is no gear-changing, so acceleration is smoother and you can hear the electric motor whining away at the rear," James said.
"When the driver's foot is taken off the pedal the bus starts to slow down, so that slowing down is also very smooth. Inside the bus, people will notice additional space, with longer leg-room and more space for buggies.
"Stops will be announced automatically over the pubic address system, which will be a big help to people who don't see well or who are blind."