And city Mayor Antonio Villaraigosa has welcomed the efforts. He says: “LA is committed to a clean truck programme that will clean and green our ports for the long haul.”

But for LA it’s not the long haul that’s the problem; rather it’s millions of short ones made by 16,000 ‘elderly’ diesel trucks between the quayside, a nearby intermodal terminal and other warehousing facilities no more than 10 miles away.

To achieve the step change in emissions, the diesel-engined tractors will be phased out in favour of the first electric ones in any port worldwide. There are likely to be fewer of them too, since the port aims to move away from its ‘one truck, one driver’ tradition to several drivers on different shifts sharing just one vehicle.

Manufacturer Balqon is poised to start building tractors that cost little more than 10 pence (20 cents) a mile to run, working on land made available by the port.

The company’s chief executive Balwinder Samra claims the typical operating costs of an electric truck could be 15% that of a fossil-fuel powered vehicle. He says: “Due to the high idling time drayage trucks typically endure, we think annual savings for truck operators could be $35,000 or more.”

His trucks can pull a 60,000lb (27 tonne) container at a maximum speed of 40 mph, and can run up to 60 miles between charges. They have been developed as part of a $5.6m investment to show the viability of electric tractors for in-terminal and on-road use.

“Smart, environmentally-friendly growth at the Port is a priority,” says Mayor Villaraigosa. “We are telling the people of our port communities that the days of big, belching black smoke are numbered. We are investing in technology that will clean our port, clear our skies, and grown green jobs.”

His vision is backed by Los Angeles Harbour Commisison president David Freeman: “Electric trucks can provide the backbone we need for a substantially cleaner drayage fleet service for our ports for years to come.”

Meanwhile, the State of Texas has awarded a grant of almost $725,000 to help manufacturer Capacity to develop a hybrid vehicle in partnership with Alternative Motive Power Systems of Ohio.

Capacity suggest cuts in emissions of up to 90% and increases in fuel efficiency of up to 70% could be achieved by its trucks, which are due to be available in the second quarter of next year.

The company is owned by Collis Industries, the largest American-owned terminal tractor manufacturer, and plans to produce a vehicle capable of running entirely on grid power or on a generator set hybrid mode, which will sustain its battery life.

Capacity President Phillip Ford says: “We are pleased to receive the grant from the State of Texas to develop a pluggable hybrid terminal tractor. The development of this product will reduce emissions at all ports, intermodal yards and distributing centre not only in North America but throughout the world. We intend to use the latest technology in electronics, engines and green propulsion."