Sooner or later, your fleet will be operating hybrid trucks. It's inevitable, given the current combination of high fuel prices and public concern for the environment.

For some, it will be a matter of image. You'll want to be seen as concerned citizens in your communities, doing what is right for the environment. It's also a marketing aid, enhancing your image among customers–government, hospitals, power plants and the like–who show their own concerns by choosing concerned vendors.

That is the basis for the EPA's Smartway program. It encourages and recognizes fleets whose owners demonstrate their concern for the environment by buying and using fuel-efficient, less-polluting vehicles and doing business with those that do. In a growing number of cities, individuals driving hybrids can use HOV (high occupant vehicle) lanes on freeways and expressways.

Financial incentives, such as tax credits and development grants, may be available to lessen the burden of acquiring new technologies. Check with your state and local governments for tax-based incentives, and search the Internet for grants and other incentives. Diesel prices above $4.50/gallon make payback for the added cost of hybrid equipment short and attractive.

The term, “hybrid,” comes from biology, when two strains of plants were combined to improve a breed. As I drive past the Midwest cornfields, I see signs for hybrid corn.


Gasoline-electric hybrids

Just as corn is bred to provide the best characteristics of each parent strain—yield-per-acre and pest-resistance, for example—a hybrid vehicle combines two technologies to get each one's advantages. Gasoline-electric is most common, combining available power of an internal combustion with energy efficiency and emissions-free operation of an electric motor. In commercial applications, diesel is more energy-efficient.

For frequent stop-and-go driving, diesel-hydraulic hybrids are being developed. Instead of using only service brakes to slow and stop, they convert the truck's kinetic energy into hydraulic pressure stored in a tank. Pressure is released to turn hydraulic motors to assist acceleration, relieving the burden on the diesel engine and reusing energy normally lost as heat from the brakes.

All hybrid systems combine power sources for acceleration and use hydraulic or electric motors for regenerative braking. The reuse of braking forces is why hybrid vehicles of all sizes and types often get better fuel economy in cities than on highways.

General Motors' full-size hybrid pickups, the Silverado and Sierra, and the SUVs built on the same platforms, the Tahoe and Yukon, get similar city and highway mileage, according to EPA estimates. They may be among the first a concrete producer might bring into its fleet. They have the same general configuration and dimensions as the conventional vehicles. But towing capacity and payload are reduced, most likely to avoid overstressing the electric motor that is inside the transmission housing.

The Chevrolet Tahoe Hybrid I drove recently has a 6.0-liter (364 cu-in) V-8 gasoline engine producing a healthy 3322 hp and 367 lb-ft of torque. At part throttle, the engine handles the 5617-lb (dry) vehicle plus payload with ease.

Under the second row of seats, so it's out of the way, sits a bank of nickel-metal hydride (NiMH) batteries. It forms the heart of the Energy Storage System. It contains batteries and a logic unit that directs 300 volts to power the vehicle, 42 volts to the electric power steering system. and 12 volts for the vehicle battery and electrical accessories.


Behind the wheel

No additional skills are needed to drive a additional skills needed drive hybrid, but there are new sensations to get used to. There is no separate starter motor to crank the engine. When starting, the electric motor engages the engine and suddenly, it is running.

If already hot, the engine may not turn over when you turn the key. Ease down on the gas pedal and the SUV starts rolling on pure electric power. The engine stays off. To accelerate more quickly, step down harder and all of a sudden, the engine is on. A computer determines which source of power is best. For really quick starts, both forms of power are blended seamlessly and optimally.

Stepping on the brakes feels different in the Tahoe. The sophisticated regenerative braking system works in tandem with the hydraulic brakes. The system uses the SUV's energy, turning the motor into a generator. The electrical energy is stored in the NiMH batteries, available when needed. A brake pedal emulator provides resistance in the brake pedal, so the feel of stopping is the same as with conventional brakes. There was a noticeable clunk each time, but only when I started braking.

One way to save fuel is to shut the engine off. That's what Auto Stop does when the engine is warm and you stop. Restarting is electric up to 30 mph. Then the V-8 blends in. When loafing along on level ground or running downhill, the computer switches off four cylinders, turning the V-8 into a V-4. When you need more power, the engine turns all cylinders back on. If I didn't see the dashboard indicator, I would not have known.

Around town, the Tahoe Hybrid's fuel economy is comparable to a four-cylinder Chevy Malibu (21 mpg vs. 22 mpg, respectively). In actual driving on a 94-mile test run, I achieved 21.6 mpg in town and 24.1 mpg on the highway. Of course, I was driving to maximize fuel economy, but those are achievable numbers.

One note of caution: Beware of high voltage. Train your technicians before letting them work on hybrids. Even 42 volts can injure, and 300 volts can kill.

Paul Abelson is a former director of the Technology and Maintenance Council of the American Trucking Association and is currently on the Board of Truck Writers of North America. E-mail truckwriter@anet.com.