I heard a brilliant story a few years ago.
There was this milk delivery truck driver. He started his shift as 6 am. He always had a partner who did most of the heavy lifting.
There was a dangerous junction on his route, entering a busy bridge on the left hand side. The visibility was nil… He could not watch the road and drive at the same time.
His partner would hang out his window to see the traffic and when it was clear, he would yell “Clear” and he would drive.
One morning his partner called in sick.