Initially I thought that for each country there would be more or less one standard or manual which set out recommended values for the geometric design of highways. After some months (which included a discussion on the topic in the Highway and Transportation Engineering Professionals group on LinkedIn). it now seems to me that countries generally fall into one of the following groups:
This is a situation where one document on standards is applicable to several countries. Examples include the standards for the Asian Highway and the UNECE standards for trans-European motorways. A multi-country standard is usually in addition to a country’s own standards and will differ from them. In other words, there will be contradictions between the different standards.
Here one country will have several competing standards. Examples include the USA, Australia and probably the UK.
One country which seems to have a particular problem of this type is Georgia. Many of Georgia’s roads were built to Russian standards. Recently Georgia adopted new standards of its own (the SST Gzebi:2009 / Georgia road design standards). Georgia has also adopted a number of different multi-country standards. For example, a 2011 presentation by Gogita Gvenetadze (Deputy Head of Transport Policy Department, Ministry of Economy and Sustainable Development) and EkaterineTsimakuridze, (Deputy Director of Land Transport Agency, Ministry of Economy and Sustainable DevelopmentofGeorgia) says that Georgia has adopted Asian highway (AH) legislation, Trans-European Motorway (TEM) legislation (and others).
There will be contradictions between the different standards.
This case is where a country’s design manual is derived from a number of different standards developed by other countries). It is not clear how such standards are prepared – do you take (for example) driver eye height from USA standards, values for side friction from Australian standards, and the dimensions of a design car from UK recommendations?
There will be differences between the standards used to compile the country’s design manual, with the implied risk of internal contradictions in the compiled document.
Contradictions in a country’s highway design standards can lead to inconsistency in design, and hence a reduction in road safety. Further, how can an engineer decide which of the standards (or at least, which of the conflicting parts of the standards) most represents best practice?