About twenty five years ago I came upon a traffic light that had fallen off of a county truck. I removed the light bulbs and used them for my front and back door entrance lights. They are still working today.
These bulbs are the standard shape screw in bulbs, but are not frosted. The glass is clear and thick The filament is a small diameter coil about 3/4 of an inch long and silver in color. There is no trademark on the bulb.
I have purchased heavy duty bulbs at the hardware store before but I believe "heavy duty" refers to the bulbs shock resistance not the life expectancy of the filament under normal use. These bulbs seem to burn out at a rate similar to standard bulbs.
The traffic signal lights must be special. Does anyone know of a source for these bulbs, other than falling traffic lights.