A fluorescent orange triangle with a reflective red border is mounted on the rear of a vehicle. What does it identify?

Correct answer: C. – Slow-moving equipment or a slow-moving vehicle
In Missouri, this triangular emblem identifies certain vehicles or equipment designed for or normally operated at less than 25 mph. State law specifies a fluorescent yellow-orange center and reflective red border. Drivers commonly encounter the emblem on farm vehicles and construction equipment and should recognize that they may be traveling much more slowly than other traffic.
Source: RSMo § 307.127.1–.2 – Slow-moving equipment, emblem required on, when — emblem described — violation, penalty — alternative display, reflective material., Missouri Driver Guide — Ch. 7, “Special Road and Traffic Conditions—Slow Moving Vehicle”

