Ted Vasser, director of student transportation for the Pittsburgh Public Schools, said he weighs many factors before recommending that schools be closed for weather-related reasons.

By noon Tuesday, with the recovery from the weekend's storm continuing and more snow on the way, all of those factors pointed to the need to close schools today for the third day in a row.

Some roads remained slick, snowy and unsafe for 14 carriers that help to transport about 24,000 city students to and from public and non-public schools each day. Some streets had only one lane open, meaning school buses would have to jockey for space with cars and other vehicles, Mr. Vasser said.

"It would just be chaotic," he said.

Sidewalks remained impassable, too, meaning students would have to walk in the streets to reach schools or bus stops. With snow piled at some stops, he said, students would have to stand in the streets until buses arrived.

Also, vans that pick up some students at their homes still couldn't thread their way through the city, and the Port Authority, which transports about 6,000 students daily, remained on a modified schedule. Mr. Vasser said some students who take Port Authority buses wouldn't be able to get to school.

District spokeswoman Ebony Pugh said several school buildings were still without power Tuesday, while about half of school parking lots still had to be cleared. Some schools rely on on-street parking for staff, and Ms. Pugh said those spaces weren't available because of snow piles.

Winter always brings challenges for Mr. Vasser, who monitors weather at home, in his office and by iPod. If morning snow is expected, he's often on the phone at 4 a.m., checking road conditions with his employees, other district workers and the Port Authority. Superintendent Mark Roosevelt has the final say on whether to delay or cancel classes.

The weekend storm, which dumped more than 20 inches of snow on the city, brought unusual challenges.

In a posting on the Shaler Area School District website, Superintendent Donald Lee said the district will "ease back into a routine to make sure students can safely adjust to arriving at school either by car, foot or bus. The definition of 'easing back in' means we will, at the very least, have 2-hour delays the rest of the week."

Depending on how much snow comes in the next 48 hours, the delays could turn into cancellations, said Dr. Lee, who toured the community with Shaler police Monday and was sobered by the cleanup work still to be done.

School cancellations create another problem -- scheduling make-up days.

Ms. Pugh said it's too early to say how Pittsburgh's calendar would be modified. Dr. Lee said he'll write a letter to the state Department of Education asking to have the cancellations forgiven because of road problems, power outages and other challenges.

"We will then be at the mercy of the officials reviewing the letter," he said.

Ms. Pugh urged parents to put the free time to productive use, saying the "educational resources and links" section of the district website offers a range of educational activities. "This is a good time for parents to do science projects with their kids," she said.

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