The big trailer: Allen Freight Trailer Bridge logs a successful first year in Puerto Rico trade with truck-and-barge service. (includes related article)

"The Big Trailer is working."

The 48-foot highway trailer is the underlying premise of Allen Freight Trailer Bridge's year-old Puerto Rico service., said Ralph W. Heim Jr., senior vice president of marine services.

"We take a big trailer that works the highways today and we put that trailer into the Puerto Rican trade," he said.

In its first year, Allen Freight Trailer Bridge has joined Sea-Barge Inc. as another small, no-frills competitor that has managed to eke out a share of the Puerto Rico trade, long dominated by Navieras de Puerto Rico, the commonwealth's government-owned carrier; Crowley Maritime Corp.; and Sea-Land Service Inc.

And, as trade lane leader Navieras' share is shaved away by talk of its privatization or liquidation by the commonwealth, each competing line stands to gain.

Current estimates of Puerto Rico's market share vary greatly, with Allen Freight Trailer Bridge figured to have between 5 and 7 percent of the business. That is as large a market share as Malcom McLean believes possible with the two barges the line is operating and explains why more equipment is needed. (See related story).

McLean operates the trailer-on-barge service like a truck line. The company controls all aspects of a shipment, quoting customers a per-mile rate between any mainland location and San Juan, rather than charging separate rates for ocean and over-the-road transportation.

By using the larger trailers, rather than the 40-foot trailers common in the trade, the company provides 37 percent more space at no extra cost. That space comes in handy, as about …