City leaders are spreading the word now: Don’t let Tuesday become Ticket Tuesday.

New parking fines and fees for downtown Lawrence are set to take effect on Tuesday. That means parking rates for Massachusetts Street meters will double. A quarter will soon buy you a half-hour when it used to buy you a full hour, a dime will be worth 12 minutes, and a nickel will be worth six minutes.

City Hall leaders have sent letters to all downtown addresses, and they hope that new plates placed on the meters clearly will spell out what the new rates are.

“We think people will pick up on it pretty quickly since it is written right there on the meters,” said Jane Pennington, director of Downtown Lawrence Inc. “I think a lot of people are like me. I can’t ever remember the rates, so I’m always having to look.”

For those looking closely right now, they’ll already notice the change at several locations downtown. City spokeswoman Lisa Patterson said crews have been out since last Wednesday reprogramming the digital parking meters.

So, technically, in many parts of downtown your quarter already is buying you half as much time. But Patterson said city parking attendants aren’t going to be sticklers about the time this week.

“This is our transition period,” Patterson said.

Before you get too excited, though, that doesn’t mean parking attendants won’t be writing some tickets this week. If motorists have clearly over-parked, even using the old rates, they’ll likely be ticketed, Patterson said.

The parking plan — approved by city commissioners earlier this summer — also includes three other major changes. They are:

• The fine for overtime parking at any meter or parking lot downtown will increase to $3, up from $2 currently.

• Hours of parking enforcement will extend to 6 p.m. Monday through Saturday. Currently, enforcement ends at 5 p.m. Enforcement will continue to begin at 9:30 a.m.

• The city will start enforcing a new habitual violator ordinance that will allow the city to charge people who have five or more parking violations within a 30-day period a $50 fine plus court costs.