Why dosen't every car have a ...

[model a vette]

Lucas (The Prince of Darkness!) made an accessory for British cars back in the 60s. It wired into the brake light circuit and would light up an indicator on the dash that said "STOP". It would flash once when you put on the turn signals so you could tell if the light on one side was out. It would go on solid when you stepped on the brakes. I disassembled the broken one on my friend's car. The unit looks like a long can style flasher with the stop lens mounted on the end. It has a pair of coils inside that use the current from the wires going to the rear bulbs to trigger tiny reed relays. It is/WAS a very fragile unit. My friend has been looking for a replacement for years.
I think the GM style fiber optics would be easier to retrofit to a rod.

[slocrow]

Why dosen't every car have a little light on the dash that shows if the brake lights are working?

It's too hard for the guy behind to see..................