BRIDGEPORT, Conn. — Tens of thousands of commuters are bracing for a difficult trip around southwest Connecticut and to New York City beginning today as workers repair the Metro-North commuter rail line crippled by a derailment and crash.

Crews will spend days rebuilding 2,000 feet of track, overhead wires and signals following the collision between two trains Friday evening that injured 72 people, Metro-North President Howard Permut said Sunday. Nine remained hospitalized.

“This amounts to the wholesale reconstruction of a two-track electrified railroad,” he said.

Several days of around-the-clock work will be required, including inspections and testing of the newly rebuilt system, Permut said. The damaged rail cars were removed from the tracks on Sunday, the first step toward making the repairs.

Service disruptions on the New Haven line between South Norwalk and New Haven are expected to continue “well into the coming week,” Permut said.

Each day, approximately 30,000 Metro-North customers use the stations where service has been shut down, according to the Metropolitan Transportation Authority, which operates Metro-North.

Amtrak service between New York and New Haven also was suspended, and there was no estimate on service restoration. Limited service was available between New Haven and Boston.

Jim Cameron, chairman of a commuter group, the Connecticut Rail Commuter Council, said he’s asked officials in numerous towns to suspend parking rules to accommodate what could be tens of thousands of motorists driving to unaffected train stations. Twelve stations are on the route that’s been shut down.

The state Department of Transportation was expected to provide details Sunday on bus service between stations on Monday. Cameron said he doubts many commuters will use three modes of transportation to get to work: driving their cars to catch a bus to get to a train station for the final leg.

Commuters will more likely rely on their cars, leading to massive traffic problems on highways that are already clogged on normal days, Cameron said. He suggested that local and regional officials post highway signs directing motorists to available parking so motorists “don’t get off the highway and drive in circles looking for where to dump their cars.”

About 700 people were on board the trains Friday evening when one heading east from New York City’s Grand Central Terminal to New Haven derailed just outside Bridgeport. It was hit by a train heading west from New Haven.

Dan Solomon, a trauma surgeon who lives in Westport and was headed to work at Yale-New Haven Hospital in New Haven, was on the train that derailed. He said he treated several injured passengers, including a woman with severely broken ankles.

He said he was in a front car that was not as badly affected as cars in the rear of the train.

“I hardly lost my iced tea,” Solomon said in an interview.

He said walls were torn off both trains and he quickly checked injured passengers to separate the most badly injured from others.

“When the EMS arrived, I was covered in everyone’s blood,” he said.

Investigators are looking at a broken section of rail to see if it is connected to the derailment and collision.

NTSB investigators arrived Saturday and are expected to be on site for seven to 10 days. They will look at the brakes and performance of the trains, the condition of the tracks, crew performance and train signal information, among other things.

The MTA operates the Metro-North Railroad, the second-largest commuter railroad in the nation. The Metro-North main lines — the Hudson, Harlem, and New Haven — run northward from New York City’s Grand Central Terminal into suburban New York and Connecticut.

The last significant train collision involving Metro-North occurred in 1988 when a train engineer was killed in Mount Vernon, N.Y., when one train empty of passengers rear-ended another, railroad officials said.