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1. The Results: Lower Costs and Improved Passenger Experience

The bright red CityTour buses rolling through Cologne's narrow streets in spring 2025 looked the same as always. But under the hood, everything had changed. Willms Touristik had just completed a retrofitting project, converting its entire 18-bus fleet from diesel to electric power. 

Each bus was stripped to its chassis, some of which were almost four decades old. The diesel engines, exhaust systems, fuel tanks and old transmissions came out. The new components went in:

• DANA TM4 SUMO HP electric motors (145 kW, 625 Nm)
• Allison T280R six-speed automatic transmissions
• Six lithium iron phosphate battery packs (240 kWh total)
  

The Allison T280R, originally developed for diesel buses and adapted for electric use, delivered exceptional benefits. Its Continuous Power Technology smoothly multiplies torque, eliminating the jerky shifts passengers feel with other systems—particularly noticeable on the upper deck. Willms deliberately opted for a transmission-equipped system rather than gearless direct drive. "We selected a drive system that has already proven itself in municipal vehicles, such as refuse collection vehicles," he said.

The Results: Lower Costs and Improved Passenger Experience

Following the retrofit, Willms Touristik experienced these results:  Energy costs dropped 45% compared to diesel. Highway driving requires only 0.75 kWh per kilometer, with average consumption around 1.1 kWh per kilometer—roughly 0.33 euros per kilometer versus 0.60 euros with diesel. Noise levels fell by up to 10 decibels. Passengers can hear tour narration more clearly without engine noise. Drivers appreciate the simplified operation: one pedal for acceleration, one for braking, while the Allison transmission handles shifting automatically.

"The acceleration is smooth, the maneuverability is excellent and there are no jolts when shifting gears. I also anticipate that the electric drive will eliminate wear and tear and high maintenance costs."
- Sacha Willms, Owner of Willms Touristik

By retrofitting rather than replacing, Willms saved resources and keept functional buses in service. The open-top CityTour buses now run almost silently through Cologne's streets, demonstrating that retrofitting can be both economically and operationally sound—particularly when paired with proven technology like Allison's automatic transmissions.