The authors Broeren, Uittenbogerd, Groot, Ruijs gave a paper at the ISHGD 2015 (5th International symposium on highway geometric design). The paper has the title “Insight in horizontal curves – fundamental research on behalf of the update of the Dutch road design guidelines”. Even before they get into their detailed discussion the authors make some interesting comments, for example:
The design of horizontal curves is incorporated in the Dutch road design guidelines for freeways (NOA) and highways (Handbook Road Design). Although the horizontal curve sections of the latest editions of these guidelines are updated, fundamental parameters and parameter values remain unchanged; vehicle and road characteristics research from the 1970s is still the foundation for the guidelines. Since modern vehicles, road pavement surface and driver characteristics can’t be compared to those of the 1970s, fundamental research is needed to determine a representative guideline on horizontal curves.
The design of ramps in interchanges in Dutch freeways is based on the design guideline NOA. Fundamentals of this guideline dealing with the horizontal alignment of ramps, originate from research of the 1970s from Pecejka (2) and Ten Cate (3). The philosophy, principles and considerations underlying these guidelines can’t be traced, resulting in a lack of fundamental backing of the current design guidelines. In addition, the contents of the current guidelines can be interpreted incorrect by the road designer, and it is not possible to deviate from the guideline on firm grounds.
(own emphasis in both)
These criticisms of Dutch road design guidelines probably apply to guidelines and standards in other countries as well. The question then is, if engineers cannot completely trust a guideline what chance is there for a safe road design?