BOSTON (CBS) – If your plan was to leave for Grandma’s on Tuesday, bad news.

“This is one of the worst days to hit the road nationally,” says Meghan Kelleher, a spokesperson for the traffic app Waze.

Wednesday or Sunday are bad too. Waze used last year’s traffic data to calculate the best advice for this year. The best days to travel are Thanksgiving day, and the Monday after.

Check: Traffic

Waze has teamed up with the City of Boston, enabling it to zero in on specific streets where the most traffic jams occur.

Last year on the Tuesday before the holiday, Harvard Street was worst, with Massachusetts Avenue running a close second. Waze auto-detected more than 9,000 traffic jams city wide that day.

Wednesday wasn’t good either. The worst street to be on was Brighton Avenue, with more than 7,000 traffic jams detected citywide.

Also on the day before Thanksgiving last year, Waze saw the highest rate of routing to supermarkets and airports than any other day of the year.

Sunday may be the worst day for the return trip. Last year, Waze detected a 240 percent increase in traffic jams nationally.

The Massachusetts Department of Transportation also has an information sharing relationship with Waze.

State Police say the worst traffic is at the Mass Pike interchanges with I-95, I-495, and I-84.

This will be the first holiday traffic period with no toll booths.

“Those choke-points that we’ve had in the past are most likely going to be significantly decreased,” said Director of Highway Safety Jeff Larason. “The hope is that we’ll see less congestion on the turnpike than we’ve seen in past years.”