After exhausted research, different sources have somewhat agreed that the symbol is used as a 'marker' to time a vehicle's rate of speed. They have been painted specifically for airborne troopers.
These symbols are said to be the official markings that meant "speed monitored by aircraft", intended to get drivers follow the speed limit. There are overhead aircraft surveillance who will clock and calculate your speed.
These systems of enforcing proper speed highway limits are common in lesser populated areas. They do this to save on actual ground patrols.
According to this Mental Floss article, “speed limit enforced by aircraft" works with the help of two officers - a pilot and a spotter.
When a vehicle crosses the start line, the spotter uses a specially-designed stopwatch to clock the car’s speed through the enforcement zone. If they determine that a vehicle is speeding, the officers in the plane radio another officer on the ground, who pulls the vehicle over and issues a ticket.
This The Globe and Mail post also agrees on how the signage works. Ontario Provincial Police Sgt. Peter Leon, said that the signage is 100 per cent accurate with plane flying 1,000 hours a year and get about 5,000 Highway Traffic Act infractions.
Familiarity with symbols on traffic signs is important for every road user in order to maintain the safety and efficiency of our transportation facilities. Here's a listing of the most commonly used traffic signs in the United States, provided by Federal Highway Administration.