You are driving a car with a fully loaded trailer equipped with overrun braking. What special aspect should be noted here?

The selected options are indeed correct as they highlight critical safety aspects of towing a trailer with an overrun braking system.

1. Longer downhill drives can lead to the trailer brakes overheating due to the continuous friction generated, which can compromise braking efficiency and safety.
2. In a stationary position on an incline, the overrun brake won't function effectively because the system relies on the forward momentum of the towing vehicle to activate the brakes. This can result in the trailer rolling back if not properly secured.
3. Activating the trailer’s parking brake before separating the vehicle combination is essential to prevent any unintended movement of the trailer once it is disconnected. This is required by law to ensure safety and stability.

Understanding these aspects is fundamental to safe towing practices and is outlined in the German Road Traffic Regulations (StVO), promoting safety for both the driver and other road users.