> It seems like everything about automating a truck would be more expensive (cost of 1 truck = 5-6 cars),
Yes, the initial cost is about that. But, the truck is directly making money whenever it's rolling, and an automated truck would presumably roll more than a driven truck, since that's an advertised feature. A car is usually only indirectly making money at best during the few hours of the day that it rolls (getting you to work, or to the park and ride).
BTW, there has been a partial solution to "trucks don't make money when the driver sleeps" problem for years. Team driving. You have two drivers, and one sleeps in the back while the other drives. That gives a truck up to 22 possible hours per day, 11 federally regulated hours per driver.
> Edit: even on 'simple' point A to point B route that involve 99% highway, what happens when a small part of the highway shuts down for whatever reason (flooding, multi-lan accident, fire, etc) and all traffic is routed on smaller adjacent streets? Automating a truck is as hard or harder than automating a car, there's no way around it.
As I mentioned elsewhere, if automated trucks are on the road, what you describe would already be solved by necessity, because you already have to go through surface streets to get you your shipper or receiver. Or, in an often imagined scenario, to get to the "freight yard" where humans would drive the first and last miles. Yes, automating a truck is at least as hard as automating a car.
The actual problem in your emergency scenario is getting the truck to follow the diversion. Right now it's cop-eyeball to trucker-eyeball communication, or even just an orange sign on a saw horse. That'll have to be worked out, plus fallbacks, but it will.