Those who refuse could be fined $25 to $50 - or even face up to 10 days in jail.
Signs are going up this week in thousands of subway cars and buses. The law has long been on the books; transit officials are now trying to get people to obey it.
Evelyn Quinones of the Bronx, who uses a walker, says people used to have better manners.
Says the 77-year old: "The world has changed."
Quinones thinks the new warnings might get the seat hogs' attention.
NEW YORK AND TRI-STATE AREA NEWS