Express mail giant FedEx Corp. is preparing to roll out the first of four new all-electric delivery trucks in Los Angeles next month, but Chief Executive Frederick Smith said there were still significant barriers to bringing large numbers of zero-emission and low-emission commercial vehicles into service quickly in the U.S.

“We would like to significantly expand the number of vehicles we have in this category,” Smith said. “But the capital costs are 50 percent higher than regular vehicles. Production hasn’t ramped up enough to bring down the expense.”

On April 9, FedEx’s new truck wrapped up a road trip from Chicago to Los Angeles along historic Route 66, with a final stop at the Santa Monica Pier.

The truck, which is slightly smaller and more rounded than the conventional FedEx delivery van, was built in Indiana by Navistar International Corp. and designed by Modec of Coventry, England. FedEx first tested a small number of similar trucks in Europe.

“It’s time for the truck manufacturing industry to create its version of the Prius: clean, affordable and widely available for truck fleets,” Smith said as a driver put the new electric truck through its paces on downtown L.A. streets last week.

FedEx said hybrid trucks improved fuel economy 42 percent, reduced greenhouse gas emissions 25 percent and cut particulate pollution 96 percent.

The FedEx fleet includes 319 diesel-electric hybrids among its 27,000 trucks in its Express division; in the Los Angeles region, 70 of the roughly 1,000 delivery trucks are hybrids.