By far the biggest advantage that a large truck has over a small truck is that a large truck has lower labour costs, per unit of cargo transported. Self-driving technologies that reduce or eliminate labour costs may therefore lead to an increased use of smaller trucks.
This could be particularly likely to occur in areas that have rugged terrain, where labour costs tend to be especially high as a result of slower driving speeds and higher insurance costs.
Small vehicles are also better at handling rugged terrain than large vehicles are. They can make sharper turns, have better control on narrow lanes, can pass through narrower tunnels or overhangs, and can manage steeper inclines.
Indeed, the biggest beneficiaries of automation might be the smallest roads of all: mountain paths that can today only be used by very small vehicles or pack animals. Very small autonomous vehicles could revolutionize transport on such paths not only by eliminating the need to pay drivers’ wages and insurance, but also by gaining more space to carry cargo as a result of no longer needing space for the driver, the steering wheel, and spare tires. These vehicles could be used to facilitate shortcut routes that pass through rugged terrain, or to open up rugged terrain to increased economic activity.
The use of small autonomous vehicles in rugged terrain might also allow for the introduction of another new technology : roll-on, roll-off ropeways. These would be ropeways that small autonomous vehicles would drive on and off of, or clip on and off of, in order to be carried above natural barriers such as steep inclines, rivers, flash-flooded roads, or snowed-in high-altitude mountain paths.
They could be especially efficient at handling inclines, not only by allowing direct as-the-crow-flies routes to replace winding, hairpin roads, but also because ropeways operate as a pulley system wherein the weight of descending vehicles does much of the work — and often does all of the work — of lifting the weight of the ascending vehicles.
Here you can see a very primitive RoRo-Ropeway at work. Here, you can see a somewhat less primitive, though still limited, version built in a Volkswagon factory in Slovakia. If automation leads to a proliferation of small autonomous cars, working ant-like to transport goods in rugged terrain, then perhaps we will see systems like these increase and improve. Economically, it may be as close as we get to flying cars anytime soon.