NEW YORK (CBSNewYork) – New Yorkers have dreaded it, Brooklyn residents have run from it – but the L train service slowdown still arrived on Friday.

For the next 15 months, commuters traveling between Brooklyn and Manhattan will need to plan ahead to avoid the major headaches coming with the MTA’s long-term tunnel repairs.

“It’s going to be a bit inconvenient on the weekends,” Armin Maneshi said.

The most recent phase of the L train improvement project will repair damage to the Canarsie tunnel caused by Superstorm Sandy.

The original plan to completely shut down the tunnel was scrapped earlier this year in favor of a partial shutdown with reduced service between the two boroughs.

In both directions on weeknights and weekends, trains will run every 20 minutes.

Within Brooklyn, east of the Bedford Avenue stop, trains will run every 10 minutes.

“It’s a relief that it’s not going to be shut down entirely so it’s the lesser of two evils,” Brittany Mylov said.

The MTA hopes that’s true and is confident in the alternatives it has planned to ease the strain.

“We’re really urging people to use it, really fast bus connections between the L train stops and the J-M-Z stops, use the G train, there’s more service,” MTA chief development officer Janno Lieber explained.

One concern is overcrowding. In popular areas like Bedford Avenue in Williamsburg, the number of people waiting could add up quickly.

“It’s going to be completely congested in the subways, obviously there’s going to be a lot of tension, a lot of angry faces coming out of the subway,” Maneshi added.

One MTA conductor worries there is a potential for chaos.

“You’re not even going to get down to the platform, you’re going to be stuck in the mezzanine waiting to get down to the platform, that’s a setup for a riot down here,” subway train conductor John Ferretti told CBS2.

Both the MTA and the Transport Workers Union Local 100 say they will monitor the situation and the MTA says it’s working closely with the NYPD to keep the subways safe.

“The biggest challenges are making sure everybody understands there’s a robust alternative service plan. We’re not starting from scratch here. You don’t have to find your way or just figure it out for yourself,” Lieber added.