I did a little research years ago, like 50, and found that as crenwelge posted there are specific requirements for lighting position.
After a certain date, ICC required marker lights for interstate trucks in addition to clearance lights. I don't know when that was. I found that in Washington State 1951 model trucks required only two cab lights and starting in 52 WA adopted the ICC configuration even for intrastate trucks. This reg no doubt varies from state to state but my cab has two lights and I pull trailers with 5 lights in the ICC configuration interstate and so far in 50 years no one in the 11 western states has said anything about it.
