All trailers and semi-trailers manufactured prior to December 1, 1993, which have an overall width of 80 inches or more and a gross vehicle weight of 10,001 pounds or more must be equipped with retroreflective sheeting or an array of reflex reflectors.
This does not include trailers that are manufactured exclusively for use as offices or dwellings, pole trailers, and trailers transported in a driveaway-towaway operation.
All trailers and semi-trailers must have the additional reflective equipment on the trucks by June 1, 2001.
Single-unit trucks (straight trucks) are not included in the final rule and therefore, do not need to meet the reflective equipment requirements. All trailers built after 1993 should have these devices and shouldn't need to be retrofitted.