Stop-Start Technology for Birmingham

Britain’s second-most-populous city, Birmingham, will soon be enjoying better air due to a number of initiatives for a cleaner city, low-emission buses among them.
Birmingham-based bus operator National Express West Midlands (NXWM), a subsidiary of the National Express Group, runs 1,500 buses providing services in Birmingham, Walsall and Wolverhampton. The company is investing millions in drastically cleaning up what comes out of the exhausts of its buses. The company’s serious commitment is also evident in its participation in the West Midlands Combined Authority Low Emission Bus Delivery Plan. In 2016 transport operators and local authorities publicly pledged to put £150 million into working in partnership to increase numbers of passengers, keep customer satisfaction high and improve air quality. “We have a responsibility within the West Midlands to try to help with the emission issues,” says Colin Saward, Head of Engineering for National Express Bus. That initiatives like these are successful is confirmed by a 2016 Greener Journeys report, which shows that across the UK, a new generation of clean buses is already saving 55,000 metric tons of greenhouse gas emissions per year, and delivering £8 million in health and environmental benefits.

Partnering with Voith in 2015, NXWM operated two buses fitted with the newly developed Voith DIWA.6 Stop-Start Technology. “We saw this as an opportunity to work with another company to reduce emissions and to improve the air quality within Birmingham,” states Saward. During normal operating conditions – including at bus stops, at red traffic lights and in heavy traffic – city buses spend up to 40% of their time in idling mode, resulting in unnecessary fuel consumption and pollution.

The DIWA.6 Stop-Start Technology requires only a software enhancement, with no need to modify the design of existing DIWA.6 transmissions. The technology automatically disengages its driveline and enables standstill times of up to 180 seconds. There is no negative influence regarding startup readiness caused by the Voith gearbox in urban city applications. The result: an impressive savings in fuel consumption of 10% to 12%, depending on application, and, as a consequence, a reduction in emissions. During the testing phase of one year in real-life conditions, NXWM was able to directly observe the effectiveness of the system. “Because we were running the two trial vehicles alongside ordinary vehicles on the same routes, we were able to compare fuel efficiency back to back. We saw savings in the region of 10% in the two Stop-Start vehicles, which is really good,” explains Saward. Next to the ecological impact, the fuel savings achieved through DIWA.6 Stop-Start also have an economic impact for bus operators, who can run their fleets more efficiently.

Passengers, drivers and pedestrians also profit, thanks to the reduced noise during stop times. “For myself and the passengers, the new Stop- Start Technology gives a much smoother ride. And for me as a driver, it is less stressful. At a stop, you just put the hand brake on, the engine shuts down and it all goes nice and quiet. You let the hand brake off and you know it will start. It is reliable, and you can just carry on,” says Andy Walcott, Driver Training Officer with National Express, recounting his experience in driving buses with DIWA.6 Stop-Start.

For National Express West Midlands, DIWA.6 Stop-Start Technology proved to be a complete success, which is why the company is expanding its fleet accordingly: “All 101 buses that we’re buying this year come with DIWA.6 gearboxes and conform with Euro 6. And 96 of those vehicles will have Stop-Start on them,” says Saward.