Your school bus is probably late.

If you have driven anything anywhere in Cambridge this week, you know why.

The school department is beginning a three-year rollout of a transportation system that provides mapping, routing and schedules for school buses and will eventually allow caregivers to access a private portal to track their children.

But that parent portal piece will be the last to come on line.

In the meantime, district chief operating officer Jim Maloney urges parents to sign up for the CPS Twitter feed to get updates.

“In an extreme situation we robocall all families to let them know of major delays,” Maloney said. An example of an extreme situation, he said, “would be if a storm hit an hour or so before dismissal times and every single bus runs late.”

They also call after-school programs, he said, when a bus is running “extremely late.”

But Wednesday afternoon, Maloney said, was “a difficult run,” and not all tweets and calls went out because “all buses were running late.”

Winter weather could cause that to situation to repeat.

“The transportation office is usually staffed until 6 p.m. and always until 5” if folks have transportation question, Maloney said. “My office is also usually staffed until 6 on school days and can be reached at Ext. 6420. Thanks for helping to get the word out.”