G.B.
Tell him to use a different way to go to work. For a very very very long time I was not able to do heavy traffic, if is much like claustrophobia. You feel like the other vehicles are closing in on you and you are trapped. The only way he is going to get his confidence back and feel good about driving is to change what he is doing. I stayed completely off the highways and drove regular streets in large cities for years. Now I see the hectic struggle many drivers do every day and am glad I have no strong desire to be one of them again.
The meds can help but his panic is coming from some trigger. I have issues with being out of town on the highway because my dad died in the Arbuckle Wilderness.
I always drove in the lane that was closest to the curb and avoided intersections where I would be trapped and could not make a right turn on red if I needed to get out of where I was. Left turns were impossible so I would go through store parking lots and other avoidance behaviors. It was odd to some but after a couple of years I was able to go back to driving by myself on the high way as long as I have my phone and could talk on it the entire way, I had a head set that fit well. I was a much better driver when I was talking too. I would find myself daydreaming if I was alone in the car and not chatting. It is no different that driving on a road trip with your best friend in the front seat except you don't have to look at them or use your hands to make a point...lol.