Up until 1988, states regulated lighting on trucks operating within each particular state. Texas for example required 2 marker amber marker lights on the top of each truck over 80" wide. The ICC regulated vehicles engaged in interstate commerce. Effective March 1989, all vehicles manufactured had to have 3 marker lights on top not over 12" apart nor less than 6" apart. At some point in time, all vehicles regardless of date of manufacture were required to comply. The 3 bar lights were a cheap way to retrofit and they are still available. There is no recommended way of attachment. Anything from pop rivets to sheet metal screws to machine bolts has been used. I have owned trucks for over 45 years and I cannot remember them not being around.
