It needs to be assessed if travelling of heavy duty vehicles at high speeds on dedicated roads is safe and by which measures it can be made safe. In the introductory post of this thread I already noted that a Car2Car communication system is necessary in order to rule out the possibility of rear-end collisions. Furthermore, all vehicles on the dedicated high-speed road should be equipped with an automatic lane keeping system in order to rule out vehicles leaving their lanes because of an inattentive driver and thus causing accidents. Such lane keeping systems already exist and are on sale.
Vehicles can also be caused to leave their lane by a tire blowout, by strong cross wind or by losing grip on a slippery road surface. Tire blowouts can be prevented by regularly checking tire profile and pressure in short intervals and meeting high safety margins. Using run-flat tires can further increase safety. Furthermore it must be ensured that no lost parts or other objects lie on the road’s surface because these can also cause a tire failure if the car collides with them. Therefore all vehicles must be tested that they can’t lose parts or that in case they do lose parts, they will immediately detect it and communicate it to the car behind so that it can stop in due time. In order to prevent people from intruding on the highway and possibly place dangerous objects on the road, the road should be fenced on both sides.
A slippery road surface can be caused by ice, snow or rain. Ice and snow rarely or never occur in most parts of the world and a high-speed road can be reasonably excused for failing to provide high-speed capability in these rare cases. The same holds for strong cross wind, which, by the way, can severely disrupt high-speed railway services, too.
Strong rainfall can cause aquaplaning. However, heavy duty vehicles are less affected by it due to their higher contact pressure per unit area. The likelihood of aquaplaning can be further reduced by running only tires with a high profile. It might be useful to build the road’s surface from drain concrete. These measures should be sufficient to deal with moderate rainfall. In case of very strong rainfall the speed would have to be reduced, just as on ordinary roads.
Altogether, by applying all these measures, a high level of satefy can be provided at a reasonable availability of high-speed capability. In very bad weather conditions safety will be provided by drastically reducing the speed, thus severly disrupting services, just like on an ordinary road. But such very bad conditions happen too rarely for justifying building a much more expensive high-speed railway or maglev just because of that, in most applications. High-speed travel on road has a reasonable availability of high-speed capability and still provides a satisfactory service level when the high-speed capability can not be provided. In case of broken down vehicles services are much less disrupted on a road because all following vehicles can go round it, albeit with a slow speed. In comparison, a high-speed rail track would be completely blocked for a long time.
German Autobahnen have no general speed limit for passenger cars and their accident record compares favorably to highways of other countries. Already today, a large part of all high-speed travel in Germany takes place on the Autobahnen, which proves that high speed travel on road is a viable alternative to high-speed rail.
