Why was the invention of barbed wire in 1874 so important to farmers

One day as your professor is driving to work, another driver runs through a red light and hits his car. the professor is shaken up but survives the accident. however, the next time he starts to enter the intersection,he becomes nervous and fearful. soon,he starts going to work via another route to avoid the intersection even though this route adds twenty minutes to his commute in each direction. according to the principles of classical conditioning, why does the professor become scared of the previously harmless intersection? what can he do about this, as going via other route is very time consuming? be specific. break down the situation into its parts and show how the principles of learning apply.