Heavy snowfall between midnight and 6 a.m. got ahead of Utah Transit Authority crews charged with clearing the platforms.

Passengers tracked snow onto the train steps, which the safety sensors read as an obstruction, said UTA spokesman Justin Jones.

"Because of the heavy buildup of snow on that first step of the trains, the sensor indicated the door was still open. It wasn't," Jones said. TRAX operators had to get out and scrape the steps before the trains would go.

And once one train got knocked off schedule, the rest followed.

TRAX was running on time by mid-morning. But the buses? "Oh boy," Jones said. Problems for buses began Wednesday night. By 10 p.m., 125 buses in Salt Lake, Davis and Weber counties were in timetable free-fall. "They were up to 3 hours late in some cases," Jones said.

Thursday morning, some buses were as late as 2 hours.

Public transit Thursday morning fought the same storm commuters braved Wednesday night. But the 6 or more inches that fell in the wee hours got ahead of snowplows and UTA platform-clearing operations.

The storm quickly overwhelmed the loads of salt plow drivers dropped to get ahead.

"There was just a lot of snow," said Utah Department of Transportation spokeswoman Bethany Eller. "At one point, there were 3 inches dropping per hour. Plows would clear the roads, then have to clear them again." UDOT had more than 150 snowplows in action along the Wasatch Front overnight. UTA had snow-clearing crews out by 4 a.m., but not enough to get to every platform multiple times, Jones said. Snow confused the train sensors only one other time in TRAX history - Nov. 26, 2004, Jones said.