The driver of a vehicle entering a highway from a private road or drive shall yield the right of way to all vehicles approaching on such highway.

The driver of a vehicle upon a highway shall yield the right of way to police or fire truck and ambulances when such vehicles are operated on official business and the driver sound audible signal of their approach.

The driver of a vehicle entering a "through highway" or a "stop intersection" shall yield the right of way to all vehicles approaching to either direction on such "through highway". Provided, that it shall not be construed as relieving the driver of any vehicle being operated on a "through highway" from the duty of driving with due regard for the safety of vehicles entering such "through highway" nor as protecting the said driver from the consequence of an arbitrary exercise off such right of way.