Soon, even Rhode Island highway signs will give directions based on what things used to be.

The state on Tuesday announced it is about to launch a three-year project to renumber all of its highway exits, starting next month on Route 295.

Just as Rhode Islanders are known for identifying places by their former names, the transition plan calls for keeping the old exit numbers with the new ones for at least a year to help motorists adjust.

The change is taking place to bring Rhode Island into compliance with a federal rule that highway exit numbers must refer to mile markers.

Like most New England states, Rhode Island has numbered its exits sequentially for decades and was slow to make the switch.

Connecticut recently renumbered exits on Route 395 to the mile-based system and is working on other highways. Massachusetts is also in the exit renumbering process.

The logic behind numbering by mile, instead of sequentially, is that it tells drivers the distance to the next exit and allows states to add new exits without having to renumber all the others. Larger states have been much quicker to embrace mile-based numbering than smaller states.

"This project will bring us in line with the rest of the country and provide more information to travelers about their location and distance to their destinations," DOT Director Peter Alviti Jr. said in a news release.

There are 11 interchanges on Route 295 and the DOT said it plans to start putting up the new numbers from north to south starting in early November and finishing before the end of the year. (A 12th interchange being built for Citizens Bank's new campus at Putnam Pike will come later.)

Route 146, which does not have any exit numbers, will begin getting them starting next year.

The DOT has not finalized when and in what order the state's other limited-access highways will get new numbers, but the entire project is expected to be finished by 2020, said agency spokesman Charles St. Martin.

The other highways being renumbered are: Routes 95, 195, 4, 10, 24, 37, 78, 403 and the T.F. Green Airport Connector.

Route 6 and Route 138 are also limited access but will remain numberless. St. Martin said this was because the roads include long sections without exits that would make the exits begin at confusingly high numbers.

Exits less than one mile apart will be given letter designations along with their new mile numbers.

The Route 295 renumbering is expected to cost $340,000, St. Martin said, but the cost of the larger project has not been determined.

The signs with arrows adjacent to each exit ramp will be replaced with versions with their new number and a smaller yellow sign below with the old exit number.

The larger highway signs with more information about each exit, usually located well in advance of the turn, will not be replaced, but be given extra panels displaying both the new and old numbers.

St. Martin said the DOT has already reached out to GPS and online-mapping companies about the renumbering and will alert them when the new numbers become official to minimize the amount of time apps have the outdated exit numbers.

One question that hasn't been answered yet is whether the renumbering project will get its own blue "RhodeWorks" project accountability sign or signs.

— panderson@providencejournal.com

(401) 277-7384

On Twitter: @PatrickAnderso_

Editor's Note: The chart listed below omits northbound Exit 3B, for Route 37 West - Phenix Avenue. It will remain Exit 3B under the new numbering system.