I double towed for eight years with a 2500 chevy/26' 5th wheel rv trailer/18' bass boat 63' total length in OK/TX/AR/MO/KS/CO. The only place I was taped for length was on a small secondary state hiway just 11 miles from home when county/state doing roadside insurance and safety check points.
JMO but it looked like state dot was training county folks what to look at with a motor vehicle/combination (proper breakaway system/length/safety chains/lights/insurance/DL/tie downs/etc.