BOSTON (WPRI) — The Massachusetts Bay Transportation Authority’s “unprecedented” month-long shutdown of the Orange Line for repairs begins Friday night.

The shutdown, from Oak Grove to Forest Hills, will begin at 9 p.m. with service resuming at 5 a.m. on Sept. 19. The line will be replaced by commuter line trains and shuttle buses.

It will not only affect subway riders, but it will also have a huge impact on the Boston area for anyone who drives, bikes, or even walks because of the added traffic from shuttle buses.

The MBTA created a guide for riders that shows them alternate routes they can take for the 20 Orange Line stations that will be affected by the shutdown.

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MassDOT also created a map warning drivers where they can expect gridlock traffic around the city. Part of the reason will be because those who rely on the MBTA will start driving if they have a car.

Additionally, some major roads in the city will be divided in half — one side for the MBTA shuttles and the other for cars — which will also cause congestion.

“It will be impossible to avoid chaos altogether, just the mere fact that this is the time of year when people are coming back to new routines in the fall will mean that people’s lives will be unpredictable,” Boston Mayor Michelle Wu said. “You can’t move that many people in different ways without all of those ways getting congestion, so you know, lots of coffee before I leave the house and lots of wine when I get home.”

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Gov. Charlie Baker said the 30-day shutdown will result in “long-term benefits on a much shorter time frame” for riders.

“These 30 days will also provide the T with the opportunity to accomplish a large amount of work that will result in substantially improved service for riders, fewer delays and faster Orange Line trips,” he said. “At the end of those 30 days, we also anticipate that the entire Orange Line will be a fleet made up primarily of new cars.”

The decision comes just weeks after flames and smoke were seen coming from an Orange Line train causing some riders to climb out windows and even one passenger to jump off the bridge into the river.

The Federal Transit Administration launched a review of Boston’s subway system in April following several accidents that led to injuries or death within the past year.