A man was struck and killed by a commuter rail train in Norwood Wednesday, officials said. The accident happened at about 4:30 p.m. on the inbound side of the Franklin Line near Washington and Dean streets, MBTA Transit Police said. Twenty-five to 30 passengers were on board, Transit Police said. The train originated at Forge Park in Franklin and was due to arrive in Boston at about 5:08 p.m. The victim was a man believed to be in his late 20s, Transit Police said. Rhiannon D’Angelo — a spokeswoman for the Massachusetts Bay Commuter Rail, which operates the commuter lines for the MBTA — said passengers were transferred to shuttle buses.