Under what circumstances can poles and timber be hauled during daytime?

The correct choice is based on the regulation that allows poles and timber to be hauled during the day if the vehicle is traveling at a speed of less than 50 mph. This requirement is in place primarily for safety reasons; when large and potentially unbalanced loads such as poles and timber are being transported, keeping the speed below this threshold helps to maintain better control and stability of the vehicle.

Driving at a more gradual speed enables the driver to react appropriately to road conditions and other vehicles, reducing the risk of accidents during transport. The focus on daytime travel is also linked to visibility—if loads are properly secured and the speed is controlled, this maximizes the safety of everyone on the road.

Other conditions regarding the combination of vehicles, city limits, and securing loads relate to different regulations or tips for safe driving but don't specifically impact the conditions under which poles and timber can be transported during the day like the speed limit does. Thus, they are not applicable to the fundamental regulation impacting daytime hauling of these types of loads.