Sitting on the train this morning I felt the usual hesitation when someone got up, leaving a seat close to me. The man in front of it didn't demonstrate any interest, so I looked around for an older person or pregnant woman, and then took the seat. Problem is, between winter wear and overweight Americans, it's hard to tell who needs a seat and who doesn't. I'm proposing a button to be distributed at OB-GYN offices, senior centers, baby stores and elsewhere that simply says:

Yes, I'd love to sit down. Thank you!

No blame, no shame, no conflicts - if someone wants or needs a seat, they're likelier to get it.