At what gross weight must trailers and semi-trailers have brakes that can be applied by the driver?

Answer: C — 4500 pounds

Trailers and semi-trailers are required to have brakes that can be applied by the driver when they reach a gross weight of 4,500 pounds or more. This requirement ensures that vehicles being towed can be safely controlled, particularly in emergency situations or when descending steep grades. Having a brake system that the driver can operate directly is essential for maintaining overall vehicle control and enhancing safety on the road. The requirement is established to minimize risks associated with heavier loads, which can create greater stopping distances and pose a higher danger to both the driver and others on the road. Understanding this point is crucial for CDL holders, as it underscores the importance of vehicle safety regulations and proper trailer operation.