With the state's switch to all-electronic tolling, drivers without an E-ZPass transponder will get charged more.

For Massachusetts drivers with an E-ZPass, rates will stay the same or go down. (You can calculate the cost of your trip with MassDOT's toll calculator.)

Don't have an E-ZPass? Don't panic. You'll have a six-month "grace period," in which you can sign up for an E-ZPass and get reimbursed for the price difference.

Here's how the grace period program works:

Drivers without an E-ZPass will receive a bill in the mail, based off of their license plate. That bill can be paid online, by phone or by visiting a customer service center. If you sign up to receive a transponder, you will be credited the difference between your bill and the lower E-ZPass rate. You can do this for any bill you receive by mail during the six-month grace period. But you must pay your bill in full first.

More details on how to be credited the difference will be on MassDOT's soon-to-launch website, EZDriveMA.com. That website goes live at 10 p.m. Friday, when all-electronic tolling goes into effect.

After the six-month "grace period," only people who are new to the area will be eligible to get a credit on their first bill.

"This is to accommodate, for example, Massachusetts’ student population," state Department of Transportation Highway Administrator Tom Tinlin told reporters Friday afternoon. "The program will forever remain in effect for first-time customers."

And a reminder: E-ZPass transponders are free.

If you already have an E-ZPass transponder, but it hasn't been activated yet, you can call the E-ZPass customer service center starting Tuesday and have your bill adjusted, according to Tinlin. (The customer service number is 1-877-627-7745.)