Italian highway officials blamed the hours-long jam, which began early Saturday, on stuck trucks and cars that set out on the A22 highway without mandatory chains ahead of a snowstorm.
Another stretch of the highway, which leads to the Brenner Pass into Austria, was also blocked for a few hours by an avalanche a few kilometers (miles) south of the border. No injuries were reported.
An Associated Press reporter on the A22 says although the traffic jam began hours earlier, the entrance ramps to the highway still weren't closed. She estimated that her car was moving north Saturday about 1 kilometer (0.6 miles) per hour.