COLORADO - The highway gridlock that some feared would mar the Democratic convention's first day did not materialize, but delegates and visitors helped fill light-rail trains traveling between downtown and hotels along the southeast and southwest rail corridors.

Traffic on Interstate 25 and other major highways into Denver was unusually light Monday morning, said Stacey Stegman, spokeswoman for the Colorado Department of Transportation.

"It was like what we see on a weekend," she said, though several accidents did slow the traffic flow at times.

The Regional Transportation District added buses to increase the frequency of shuttle service on the 16th Street Mall, said agency spokeswoman Daria Serna.

Large crowds of delegates, convention visitors and activists roamed the mall throughout the day, shopping at vendors' stalls, spilling into the bus lanes and causing several brief halts to shuttle-bus service.

"We're going slower, giving them a little more warning bell and anticipating that they will walk in front of the bus," said Russ Nipper, who's been driving RTD shuttles on the mall for 25 years.