32-15-20. Slow-moving vehicle emblem required--Place of mounting--Violation as petty offense. All farm machinery, including animal drawn vehicles, and highway construction and maintenance vehicles which are designed for operation at a rate of speed of twenty-five miles per hour or less or such vehicles when operated at speeds of twenty-five miles per hour or less, when operated on a public highway, shall display a slow-moving vehicle emblem. Said slow-moving vehicle emblem shall be mounted on the rear of a slow-moving vehicle in such a position and condition as to be clearly visible. A violation of this section is a petty offense.