By Brad Segall

NORRISTOWN, Pa. (CBS) — With the mercury expected to drop to near zero overnight in Philadelphia and its surrounding suburbs (see related story), what goes into making sure those yellow school buses run on time in the morning?

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Some suburban school districts have their own buses; others contract out with bus companies.  But in most if not all cases, those buses run on diesel, and during the winter months they’re plugged in at night to keep the engine blocks warm.

That also helps them start on cold mornings.

In the Centennial School District, in Bucks County, spokeswoman Andrea Didio says mechanics will be coming in a little earlier.

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“Depending on the prediction of the weather,”  she told KYW Newsradio today, “we would bring our mechanics in an hour or so early and they would go around and start up all the buses and check to see if there are any issues with any of those buses.”

That gives them enough time to fix any problems before their fleet of buses hit the roads shortly after 6:00am.

Looking back, she says, the district hasn’t really had any problems on colder-than-usual mornings.

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