I'm a former over the road truck driver who hauled truckload freight.
I disagree profoundly that self driving trucks are the future, the future is multimodal transport, even now a significant proportion of long haul (greater than 3-600 miles) is already on the rail, either in the form of a container or piggyback.
The issue that keeps the remaining long haul (greater than 600 miles) on the road (vs rail) is timing, when you put something on the rail, you loose a day or so at one end in loading/classifying and another in classifying/unloading. That time loss is something that in all but a few situations can be accommodated for by extra planning - but it requires the planning and consent of the shipper and consignee to do so - the trucking and rail companies are already on board as shipping by rail is much cheaper/easier.
For LTL companies, most of their drivers only run from terminal to terminal, and the distance driven and time spent is much much lower, but even with them, a crossdock transload facility where one side is a truck dock, and the other is a railcar could for example cut down on some logistics pain - but it still would incur additional delay due to the machinations required by the railroad to switch and deliver cars in their network.
Another complicating factor is reefers, right now each refer either has a generator attached (for containers) to it powered by diesel fuel, or has a diesel powered refrigeration unit on the trailer - this for the rail could be replaced by freight trains with HEP (head end power) to power the refrigeration units - but to do so requires a sizable investment by everyone involved (rail cars that support such a system, cans and trailers that support such a system, and transit yards that can supply the power to keep everything cold)
Even with the challenges, in 20-30 years, I'd expect only 10% of truckload miles to be actually hauled end to end by a truck, the rest of it should go on the rail, then be carried the proverbial last mile (in reality couple hundred miles) by a truck.
As a former driver, in my opinion the issue is not the HOS (hours of service) rules, its the way companies, especially many smaller ones dispatch their drivers - you can be expected to go from working days, to working nights instantly, and it can really fuck hardcore with your sleep schedule.