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.