The MBTA South Coast Rail project modernized more than seven miles of existing track, constructed two new layover facilities and built six commuter rail stations. Despite repeated delays, the Massachusetts Bay Transportation Authority’s South Coast Rail is back in service after more than 65 years.

Like all other Commuter Rail trips, the first train Monday morning on the MBTA’s new Fall River/New Bedford line set off with a jolt. But unlike the rest, it was followed by an unfamiliar sound for the early hour: applause.