Wipers move fast across the screen and may, in some way, represent a threat, or just 'fun' given how many dog like to chase anything that moves.
I think you'd do well to travel with your dog in a crate at the rear of the car. Having one 'going nuts' like that, when in a moving car, could surely be very dangerous, if not distracting!!
What idiots are hitting the TD button for answers who suggest ALL dogs should be properly confined in a moving car? Or do you think it's fun to have a dog misbehaving in a car, and potentially causing an accident/crash!