There are many different parameters involved in the design of a highway. So far I have a list of more than 230, and I am still adding to it. Some parameters are related to and perhaps derived from others – so for example, differential speed is related to if not also derived from design speed.
If we can use the idea of “relationships” to give a structure to the many design parameters, it may be possible to get a better understanding of what we are doing. In theory we could arrange the different parameters into several layers of detail (1st level parameters, 2nd level parameters, 3rd …, 4th …. etc). But the first question is to state what the fundamental parameters are. At the present time I would suggest there are seven (possibly eight) :
1 Road type
2 Vehicle type
3 Road users
8 Aesthetics (?)
Maybe brief notes on each of these parameters could take the discussion further.