Well... there's a button on the door of my car. As long as the key's in my pocket, pushing the button either locks it or unlocks it dependent on it's current state. Then I get in and - lo! - there's a button on the dash which closes the power relays if the car is switched off, or opens them if it's switched on. I think this sort of logic is common to most modern cars, but I will admit that I am only assuming that somewhere in a multi-billion pound development project they found a budget to check that people found that sort of logic intuitive.
Every single car key fob I've seen in recent years (at least those offering remote central locking) has both a lock and unlock button and frequently another button to release the boot lid or perform some other function. Internally usually a rocker switch in my experience - one way to lock, t'other to unlock. I've yet to spot any braille on a car door controls...
I do agree that train doors only really need an 'open' button - it is what London Underground supply, even though many people still haven't realised they are rarely, if ever, in use.
On the subject of door buttons, I do find the inter carriage door open buttons in the new 387's very odd - they appear to be in a different position and of a different size in each coach...