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Saf-T-Liner® C2 Hybrid

A bus that saves energy—and uses it again.


Thomas Built has a role to play when it comes to taking care of the earth. That role is helping reduce emissions and lower dependence on fossil fuels through alternative powered buses. The idea of a greener future is nothing new at our company. Daimler developed its first hybrid bus, the Mercedes OE302, back in 1969, and Daimler remains the world leader in green technology today. That extensive research and experience uniquely positions Thomas Built to provide innovative hybrid solutions, like our first hybrid electric vehicle, the Saf-T-Liner C2e. Introduced to the market in 2007, the C2e is based on Eaton's hybrid electric parallel system, which is powered by both a diesel engine and an electric motor/generator. The forward-thinking design and engineering is carried over from our innovative Saf-T-Liner® C2.


Fast Facts
Seating Capacity
  • Up to 81
  • 33,000 lbs.
  • Eaton automated manual transmission
Electric Drive
  • Electric motor: output 44kW
  • Generator output: 44kW
Drive System
  • Eaton parallel hybrid drive system/diesel-electric
Diesel Engine
  • Cummins ISB six-cylinder in-line engine
  • Emissions meet EPA '07 (will meet EPA '10)
  • 6.7 liter displacement
  • Optional B20 compatibility
  • Output of 200 HP rating with 520 ft-lb torque at 1600 RPM
Battery Pack
  • Lithium-ion batteries, capacity 1.9kW/h

A system that makes sense. Perfect, clean, efficient sense.

In the stop-and-go world of school bus driving, Thomas Built's Saf-T-Liner® C2e hybrid electric parallel system makes perfect sense. You gain fuel efficiency by using energy that's normally lost in braking.

Because the engine doesn't have to work as hard, it releases fewer emissions. That leads to cleaner air, lower dependence on fossil fuels, and up to 30% reduction in greenhouse gases.

Hybrid Features Customer Benefits
Electric motor launch and acceleration assist
  • Increases fuel economy
  • Reduces emissions
Regenerative braking
  • Aids in braking
  • Reduces brake wear
Charge-sustaining battery system
(vs. depleting system)
  • Charges without plug or electrical outlet
  • Requires smaller battery system
  • Less vehicle weight due to lighter batteries
Parallel system
(engine-only operation if hybrid goes offline)
  • Increases reliability as both electric-diesel or diesel-only operation are available
Engine start from electric motor
  • Starts more quickly
  • Reduces engine starter wear
  • Increases reliability

How It Works

See how your bus stops add power.

The Saf-T-Liner® C2e is an electric parallel drive system. Simply put, a hybrid system is added alongside the conventional powertrain already in use today. You don't have to plug it in. Rather, the hybrid electric drive system generates electric power and stores it in the hybrid batteries when the bus' brakes are applied. The vehicle uses this stored energy to add power back into the motor/generator when the throttle is depressed.

The system consists of these components:

  • Hybrid drive unit (HDU)
  • Power electronics carrier (PEC)
  • Motor inverter/controller
  • Hybrid cooling system
  • Cummins ISB engine
Eaton Hybrid Drive System
Hybrid Drive System Diagram
  1. An electric motor/generator mounted between the engine and the transmission generates electric power.
  2. Power is stored in the lithium-ion battery when the bus is coasting or brakes are applied.
  3. The vehicle uses stored energy to add power back into the transmission when the throttle is depressed.
  4. If the hybrid system goes offline for any reason, the bus automatically switches to the conventional powertrain system.


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