NORTH ATTLEBORO, MA – This past summer, the Port of Los Angeles saw an unusual sight — an electric truck ferrying containers from terminals to warehouses and rail yards. The truck, a prototype vehicle, was a short-haul drayage truck capable of pulling a 60,000-pound cargo container at a top speed of 40 miles an hour. The experimental truck, which produces zero emissions, has been greeted with enthusiasm in California, which has adopted a number of regulations to improve air quality, according to www.dcvelocity.com.

Testing of the prototype, which was manufactured by Balqon Corp. of Santa Ana, Calif., is still under way. The port planned to put the truck into regular service to see how it would hold up under the daily stress of draying loads. However, early results have been sufficiently encouraging that the port has already decided to purchase five more of the vehicles, which cost about $208,000 apiece.

When loaded, the prototype vehicle being tested in Los Angeles can go only 30 miles before needing a battery charge. Unloaded trucks can travel up to 60 miles without a recharge.

The hybrid trucks currently on the market use what’s known as “parallel electric” technology — the same technology that powers passenger cars like the Toyota Prius. These vehicles also save energy in stop-and-go driving through “regenerative braking,” a technology that allows the vehicle to capture energy when the driver brakes and store that energy in a battery for reuse in restarting and low-speed operation.

In North America, Navistar International of Warrenville, Ill., started manufacturing hybrid Class 6 and 7 trucks a year ago. At low speeds, the truck is powered by an electric engine, and at 25 miles an hour, the diesel engine kicks in. The company has sold 200 of these hybrid commercial trucks, which command a premium price compared to traditional vehicles. A traditional Class 6 or 7 truck goes for $45,000 to $60,000, depending on the specifications, while a hybrid unit costs somewhere between $80,000 and $90,000. However, fuel savings help offset some of the price differential between a regular truck, according to www.dcvelocity.com.

Early this year, Freightliner of Portland, Ore., announced that it, too, was beginning production on a hybrid medium-duty truck — the M2 106, a Class 6 truck designed for hauling beverages. The company, which is part of Daimler Trucks North America LLC, said it’s seeing a lot of people “pulling the trigger on orders now.”

Peterbilt Motors Co. of Denton, Texas, has also announced plans to begin making medium-duty dieselhybrid vehicles. A plant in Ste. Therese, Quebec, began production on both a Class 6 and a Class 7 hybrid truck this summer. The two models use a parallel hybrid system with an electric motor alongside a diesel engine. A Peterbilt spokesman said that a wine distributor in California has already placed an order for the hybrid diesel trucks, which it plans to begin using this fall.

Peterbilt also has plans to scale up hybrids to Class 8. The Texas truck maker is currently working with Wal-Mart Stores to develop a Class 8 prototype. After the tests with Wal-Mart are finished, the company will decide whether to take the Class 8 hybrid truck into production.

With the era of cheap oil apparently over, truck manufacturers will most likely continue to experiment with technology and develop variations on hybrid trucks of all shapes and sizes. In the meantime, though, American truck manufacturers are gearing up for a surge in sales of medium-sized hybrid electric trucks.