"Road tractor" includes every motor vehicle designed and used primarily as a road building vehicle in drawing road building machinery and devices.
[ 1961 c 12 s 46.04.490. Prior: 1959 c 49 s 53; prior: (i) 1943 c 153 s 1, part; 1937 c 188 s 1, part; Rem. Supp. 1943 s 6312-1, part. (ii) 1937 c 189 s 1, part; RRS s 6360-1, part.]