Reversing transmission (reverse gear unit) instead of turning area: Dual cabin buses with Allison automatic transmissions bring tourists to Mont-Saint-Michel

Since April Veolia Transport has operated six dual cabin buses produced by Contrac GmbH for shuttling visitors to Mont-Saint-Michel. Each of these unique vehicles has two driver cabins while a special gear module reverses the direction of transmission output so the buses can change direction without turning.

MAINZ, Germany – With about 3 million visitors per year, the Mont-Saint-Michel monastery is one of the greatest tourist attractions in France. Prior to this year, visitors arriving in cars and coaches were required to park on the narrow road leading to a small island in the Wadden Sea of Normandy. Today, traffic has to stay on dry land and only shuttle buses bring tourists to the monastery. That sounds easy, but it was a huge technical challenge because there is no place for buses to turnaround at Mont-Saint-Michel. Bus manufacturer, Contrac GmbH from Wiesbaden, Germany, came up with an idea for a unique dual cabin bus.

Moving forward with intelligent solutions

“At Mont-Saint-Michel there are many similarities to an airport. As many passengers as possible must be transported within a short time over a relatively short distance,” explains Rüdiger Hömberg, who led the project at Contrac GmbH. “As a leading manufacturer of airport buses, we won the Europe-wide tender to produce the vehicles based on our experience and creative concept.”

The Cobus DES named “Le Passeur” is based on the Cobus 2500, a 12.3 m long airport bus, which is equipped with an Allison 2100 fully automatic transmission. Two fully functional driver cabins with one common drivetrain allow two-directional operation.

DGS from Mainz, Allison’s main distributor in Germany, played a major role in creating this innovative drive solution. DGS developed a special reversing drop-box module, which is directly mounted on the Allison automatic transmission and reverses vehicle direction without affecting the drivability. This compact and short design had a minimal impact on overall driveline length. Direction change occurs when the vehicle is at a standstill. The drop-box is engaged pneumatically from the driver’s cabin in use.

Development of the reversing transmission took about six months including construction of the first unit. The new reversing transmission can be combined with any Allison 1000 and 2000 Series fully automatic transmission.

“Due to the positive experiences we have had with Allison since 1990, we decided to equip the new Cobus DES with an Allison fully automatic transmission. I was positively surprised that DGS in Mainz was able to deliver the reversing module. We have always been very satisfied with DGS concerning competence, service and reliability,” says Hömberg.

The Allison 2100 transmission in “Le Passeur” is designed for vehicles up to 13,600 kg gross weight and engines rated up to 300 HP (224 kW). The advanced electronic controls offer diagnostics features while providing excellent shift quality, improved passenger comfort, and increased fuel efficiency.

The maximum speed of the shuttle buses at Mont-Saint-Michel is 70 km/h, but they are electronically regulated down to 50 km/h; while on the bridge they may only drive at a speed of 25 km/h.

On April 28, 2012 the local transport operator Veolia Transport Mont-Saint-Michel put the first six shuttle buses in operation. Over the next 12 years, each vehicle is expected to cover about 600,000 km exclusively in shuttle service.

Safety and registration

The shuttle buses also run on public streets, so it was necessary to design bow and stern in such a way that the driving direction is immediately recognizable for all road users.

Rüdiger Hömberg explains, “At the beginning, developing a vehicle for such an application sounded easy. But many challenges had to be overcome to enable a legal registration of the vehicle for two-directional operation on public roads.” Thanks to the special construction, reflectors can automatically be switched between white and red at direction changes, and the exterior rear-view mirrors can be retracted.

The Contrac dual cabin bus is extraordinary in many ways. It’s technically advanced because of the two-directional operation and the huge space for up to 90 passengers. Aesthetically its look with maritime outside cladding made out of 7 mm teakwood is unique.

Further applications are planned for these buses with requests from bus operators in Southern France, who want to operate such a vehicle with an open or fully glazed roof for city tours. In addition, there is interest in the two-directional vehicles for substitute transportation at construction sites with blind alleys. “For this purpose, however, the dimensions of the vehicle must be adjusted,” says Hömberg.

The mountain will again become an island

Since 1979, Mont-Saint-Michel has been a part of the UNESCO World Heritage. Without buildings the rock is about 46 m high, and its immense bay is impacted by Europe’s strongest tides. The location is famous for its Benedictine monastery which has now become an increasingly popular place of pilgrimage.

As a result of the road embankment built in 1869 the bay of Mont-Saint-Michel was filled with silt. To restore the original conditions, an ambitious renewal project (called the “Renaturation Project”) was established. The plans involve removing the road embankment and replacing it with a stilt bridge, which will be completely closed to individual traffic. Under the bridge piers, the water will flow freely so that Mont-Saint-Michel will again become a real island.

Jul 23, 2012

About Allison Transmission

Allison Transmission (NYSE: ALSN) is the world’s largest manufacturer of fully automatic transmissions for medium- and heavy-duty commercial vehicles and is a leader in electric hybrid-propulsion systems for city buses. Allison transmissions are used in a variety of applications including refuse, construction, fire, distribution, bus, motorhomes, defense and energy. Founded in 1915, the company is headquartered in Indianapolis, Indiana, USA and employs approximately 2,700 people worldwide. With a market presence in more than 80 countries, Allison has regional headquarters in the Netherlands, China and Brazil with manufacturing facilities in the U.S., Hungary and India. Allison also has approximately 1,400 independent distributor and dealer locations worldwide. For more information, visit