Final answer:
Trailers and semitrailers must have brakes that can be applied by the driver when the gross weight of the trailer exceeds a certain limit, typically ranging from 4,500 pounds (2,041 kilograms) to 15,000 pounds (6,804 kilograms).
Step-by-step explanation:
Trailers and semitrailers must ordinarily have brakes that can be applied by the driver when the gross weight of the trailer exceeds a certain limit. This limit is generally specified by laws and regulations in different countries, but typically it ranges from 4,500 pounds (2,041 kilograms) to 15,000 pounds (6,804 kilograms) for trailers.
For example, in the United States, trailers with a gross weight of more than 3,000 pounds (1,361 kilograms) are required to have brakes that can be operated by the driver.
It is important to note that the specific weight limit for requiring trailer brakes may vary depending on the jurisdiction and the type of vehicle being towed.