Final answer:
In case of a daytime highway breakdown, the driver should activate hazard lights, safely pull over, set out emergency signals.
Step-by-step explanation:
When a truck breaks down on a highway in the daytime, the driver should immediately activate the hazard lights to alert other drivers. Then, if it's safe to do so, the driver should maneuver the truck onto the shoulder of the road, away from traffic.
After the vehicle is secured, the driver should set out emergency flares or triangles at a distance behind the truck to provide a warning to oncoming traffic. This is to ensure safety and to give other vehicles enough warning to slow down or change lanes.
Additionally, the driver should stay with the vehicle if it's safe, call for roadside assistance, and wait for professional help to arrive. It's critical that the driver does not attempt to fix the truck on the active highway, as this poses a significant danger both to the driver and to passing motorists.