Riders of the strikebound Long Island Railroad, the nation's busiest commuter line, endured 4 1/2 hours of jammed subways and clogged highways during the morning rush hour yesterday, the first workday of the strike.

For the 188,000 people who use the deficit-ridden line each day -- one quarter of all Americans who commute to work by train -- the morning rush hour began at 5:30 a.m. and continued past 10 a.m.

In other words, a railroad spokesman said, "The rush hour began 2 1/2 hours early and lasted an hour later."

No new talks were scheduled in the strike, which began at 12:10 a.m. Saturday, although the National Mediation Board said it would try to get both sides back to the bargaining table by Wednesday.

In the strike's first rush hour, thousands of commuters left cars at parking fields and LIRR stations in the suburbs and boarded special buses to Manhattan. Others drove into some of New York City's outlying boroughs, where they jammed into subways.

At one bus stop, at Roosevelt Raceway in suburban Westbury, commuters lined up for more than half a mile waiting for buses to Manhattan. The raceway parking lot looked the way it does the day of a big race.