It may be better for the roads, but it may be overall worse for the environment and/or shipping costs.

Building an entire truck isn't free from cost and environmental impact, nor is maintaining it.

Fuel usage also increases with more trucks.

There's also an overhead each truck has that scales differently from how much it lugs, based on fuel it needs to carry and space for its driver.

True, reducing the cargo would require more trucks to carry the same load, increasing demand for truck drivers.

On the other hand, wouldn’t reducing the amount of cargo a single truck can carry makey individual truck driver less valuable?

The end result would probably depend on a lot of other factors, including the supply and demand curves for alternative forms of transportation (trains, boats, investment in autonomous solutions), as well as the supply and demand curves of the goods being transported (because if the cost goes up to pay for more truck drivers, maybe people will just stop buying that product).

Lots of ways to cut that. Consider pounds-mile/gal for freight on my 80k truck carrying 45k freight, vs your vanagon or beemer.

My truck gets at least 6mpg, usually 7.5, sometimes 9, and I've seen 10 once.

Or for the companies who will own/lease the automated fleets, foregoing having to pay wages, health insurance, vacation time, or work breaks allowing them to ship quicker since they aren't forced to stop driving and take a break every x hours. You'll just get a smug smile and a "learn to code" line.

No, for the roads it would be better to have the weight distributed on more "area", hence: more wheels and bigger wheels for the same weight. And this does _not_ require more trucks, just more wheels below each truck.

However, an even more material-efficient solution would be to use railways instead.