What is the primary purpose of signs on the back of slow-moving vehicles?

The primary purpose of signs on the back of slow-moving vehicles is to alert drivers of the presence and speed of the vehicle ahead. These signs are crucial in enhancing road safety, particularly for vehicles that may not be traveling at the same speed as regular traffic, such as agricultural machinery or construction vehicles. By providing this alert, drivers can maintain a safe following distance and make informed decisions about overtaking or adjusting their speed, thereby reducing the risk of collisions.

In this context, options that suggest unrelated purposes, such as informing drivers of safety tips, encouraging speeding, or marking the end of road works, do not address the specific function of slow-moving vehicle signs. Each of these alternatives fails to align with the key safety objective that these signs serve on the roads, which focuses on maintaining awareness and preventing accidents due to unexpected slow-moving vehicles.