BART riders could be fined for taking up more than one seat, under a proposal to be considered by the agency's board of directors on Thursday.

The ordinance introduced by BART director Joel Keller specifies a fine of $100 for a first offense, increasing to $500 for repeat offenses.

Exempt would be those who, because of "soma type or physique" or medical condition, must occupy more than one seat. But a rider who prevents another person from sitting by parking possessions on an adjacent seat or by sprawling or "manspreading" would be in violation.

The ordinance cites the greater risk of injury to standing riders, as well as "fatigue, discomfort, altercations and occasionally medical emergencies."