Where i live the front six seats on the buses are for those with mobility problems mothers with prams etc.I never sit there myself.
These six seats face the aisle of the bus and fold up to accommodate prams and wheelchairs.
But i often see people just get up and move to the back of the bus without saying anything when someone gets on who looks like they need a seat.
An option to offer your seat but not verbally.The person can sit or not sit.