An expert in ship rescues says the vessels assigned to escort Alaska's oil- tanker fleet may not be able to rescue tankers stranded in the Gulf of Alaska in bad weather, and that deploying some tankers' towing equipment, designed for use in just such conditions, could take anywhere from several hours to two days.

Jan ter Haar said in a study released Monday, however, that the escort vessels should be able to safely steer their charges through Prince William Sound.It's unclear how serious the deployment of emergency towing equipment could be, said two Alaskans who helped coordinate the new study. The equipment has been required since an incident in the early 1980s involving a drifting tanker.

Robert Levine of Arco Marine Inc. and Tex Edwards, a member of a tanker watchdog group, said they were unsure if rescue tugs now can use their own towing equipment in such an emergency.

After the 1989 Exxon Valdez oil spill, the oil industry spent tens of millions of dollars to buy more spill cleanup equipment and provide extra escort vessels for tankers in Alaska.

The recent study was designed to determine if the safeguards put in place after the Exxon disaster are adequate to prevent another spill.

Mr. ter Haar did the study for oil shipping and transportation companies, government regulators and the Prince William Sound Regional Citizens' Advisory Council or RCAC, a citizens' watchdog group set up after the Exxon accident.

Mr. ter Haar is a "towing master" with years of experience rescuing imperiled ships.

Mr. ter Haar's study is just the first half of the evaluation; the other half will include computer simulations of bad-weather rescues to test the abilities of various types of rescue vessels in bad weather. That portion is expected to be completed in the spring.

A big question the study will answer is whether more versatile "tractor" tugs are needed in Prince William Sound. Mr. ter Haar said conventional tugs are adequate, but Mr. Edwards and Mr. Levine said they didn't think a decision could be made until the entire evaluation is done.

Mr. Edwards said Mr. ter Haar's expertise is in open-water rescues, not working in tight quarters, as exist in the Valdez Narrows.

Mr. ter Haar also recommended a larger tug be purchased for Gulf of Alaska rescues. Mr. Levine, who said a decision on such tugs also should wait until the evaluation is complete, said the larger tugs might cost as much as $25 million to build.