An on-duty MTA bus driver stabbed another motorist in Queens when he realized the man behind the wheel was actually the guy who had been messing around with his wife, sources said.

The driver of the Q52 bus was on his route in Arverne around 1:30 p.m. Tuesday when he spotted the 48-year-old Oscar Williams driving his Honda near the intersection of Beach Channel Drive and Beach 67th Street.

That’s when the MTA employee abandoned the empty bus and charged up to Williams’ car, where the two men squared off in the middle of the street before the driver stabbed his rival with a small pocket knife, sources said.

“There was a lot of blood coming from his arm,” said a local deli owner who witnessed the fight. “Someone tied it with a do-rag.”

Williams flagged down two cops on patrol, who quickly cuffed the scorned husband and dragged him down to the 100th Precinct where he is awaiting charges.

Williams was treated at Jamaica Hospital for minor injuries.

Sources said the two men were mixed up in a love triangle that involved the bus driver’s wife, adding that the dispute between the two had been going on for a while.