Road lighting tenders and engineering specifications routinely reference "M1" or "M3" without explaining what those labels actually mean or where the numbers come from—and getting the classification wrong on a bid can mean a rejected submission or an underperforming installation. This reference guide explains where the M-class system originates, what each class actually requires in measurable terms, how a road gets assigned to a class in the first place, and how the classification connects to the wattage and pole spacing decisions you'll eventually make for a solar street lighting project—written for engineers, EPC bid teams, and government buyers who need to work with these standards directly rather than take a supplier's word for it.