In recent posts I have discussed the idea of the “technical environment” for road design. One of the seven technical factors which I suggest describe this environment is “road type”.
By road type I mean more than “road hierarchy” – in fact I believe that this particular term has lost much of its value. A road type refers to a road which by its nature and use needs specific design standards of its own. Examples might include port roads, gravel roads, or streets. In fact, separate design standards already exist for (at least) these three road types.
The following table is a first attempt to list road types. You will see that it includes “roads in tunnel” and “roads on bridges”. This is because some geometric design values are specific to these road types (for example, the normal value for the gradient of a motorway is not the same as the value of gradient for a motorway section in a tunnel).
There already seems to be a move towards the development of geometric design standards for different road types, perhaps out of exasperation of the lack of appropriate detail in more conventional road design standards.
306 – UK, Lancashire CC: “Functional road hierarchy strategy”; 2002
726 – multi-country, UNECE “Trans European Motorway standards and recommended practice third edition”; 2002
1101 – Malawi, Roads Authority Malawi, “Preparation of a Pavement Design Manual and Standard Bidding Documents for Low Volume Sealed Roads in Malawi – Inception Report; 2013
1142 – Ireland, COFORD national council for forest research and development, “Forest road manual”; 2004
2211 – general, AFCAP, “Geometric design and safety for LVRR”, presentation by Dr. John Rolt, date ?
2273 – USA, Virginia DOT, “Virginia road design manual, A: geometric design”, 2015
Notes: ref. 306 mentions the road types indicated, the others indicate some detailed design guidelines