The high percentage of inland shipping accidents caused by human error underlines the need for crews working on U.S. tugs and towboats to be licensed by the U.S. Coast Guard, a leading maritime labor union said.

"Seamen with merchant mariner documents have a better safety record and are less susceptible to injury and death than men and women working aboard tugs and tows" who don't meet Coast Guard standards, the Seafarers International Union said in a new safety study.The union has been lobbying for licensing legislation for several years. It has stepped up its campaign since the Sept. 22 derailment of Amtrak's Sunset Limited on a bridge near Mobile, Ala.

The union reached its conclusion about licensing after studying Coast Guard data on casualties and maritime accidents. The data shows that between the late 1970s and mid-1991, human factors caused 58 percent of tug and tow boat accidents.

In contrast, human factors accounted for 36 percent of accidents on Great Lakes vessels and 31 percent of accidents on deep-sea vessels, the study showed. The Coast Guard licenses most crews on ocean and Great Lakes vessels.

On those vessels, the Coast Guard data shows that the primary cause of accidents are vessel-related. Those problems are defined as equipment and material failures not related to improper maintenance.

In all three vessel types, the percentage of accidents caused by environmental factors and forces of nature was about the same. The results of the union's analysis of Coast Guard data were published in the November issue of the Seafarers' newspaper.

A preliminary investigation has concluded that the Amtrak Mobile accident, which killed 47 people, occurred shortly after a barge, lost in the fog, rammed the bridge and knocked it out of alignment. The towboat pushing the barge did not carry charts, compasses or other navigational tools required by the Coast Guard on Great Lakes and ocean vessels.

The investigation has not yet released its final results.

Under current law, crewmembers on inland towing and harbor towing vessels, as well as ocean and harbor tugs of less than 100 gross tons, are not required to hold Coast Guard merchant mariner documents.

That means that "the vast majority of tugs and tows, many having engines with horsepower in the tens of thousands, some pulling more than 50 barges at a time," are not documented by the Coast Guard, the SIU said.

Great Lakes and ocean vessel crews licensed by the Coast Guard are subject to numerous regulations, including drug and alcohol testing, reviews of their

criminal records and Federal Bureau of Investigation checks, the SIU said.

The SIU is backing legislation to require men and women sailing on inland vessels of more than five gross tons to acquire a merchant marine license from the Coast Guard. Similar legislation passed the House last year, but Congress adjourned before the Senate voted on the bill.

"For the last two years, the SIU has insisted that a potential for catastrophe exists on the nation's inland waterways," said Terry Turner, the Seafarers' national director of governmental relations, in recent testimony before a House subcommittee. "No longer is this prophetic; the Sunset Limited has made it all too real."