OAKLAND (KRON) — Get ready to pay a fine if you take up too much room on BART.

The BART seat hog law officially went into effect on Thursday.

This means riders who take up more than one seat on a train during the most crowded times could face fines and could even be arrested if they have multiple violations.

First-time offenders will have their names entered into a database and be given a verbal warning.

A second offense will cost you $100 and the tickets go up from there.

People whose size or medical condition requires them to take more than one seat will be exempt.

BART police will enforce the ordinance weekdays from 6 a.m. to 10 a.m. and 3 p.m. to 7:30 p.m.