More notes on road design standards (1)

Many countries publish “standards“, notes, advice and requirements related to the geometric design of roads. But as I have argued before (see for example here) there are too many of these standards. What makes life more difficult for engineers is that most of these standards suffer from one or more of the following problems:

  1. Traceability

A standard may suggest values for a parameter such as “side friction” – but does not say where the values come from. For all the reader may know, they may be based on research made in another country almost a century earlier. The reader should be able to trace back the suggested values to their original source.

  1. Completeness

The information presented may be incomplete. To take “side friction”  as an example again, perhaps the standard only gives values for one vehicle type, or the accompanying notes forget to mention that correction factors were applied to observed values.

  1. Terminology

The standard may not define the terms which it uses. For example, perhaps the values suggested for side friction refer to wet , surfaced roads, and are “maximum side friction factors accepted for design purposes” (or desirable maximum, or whatever).

  1. Inconsistency

Occasionally a standard may give different values for the same parameter, either internally or where the standard is part of a series of documents.

  1. Findability

Sometimes, suggested values are hidden in a dense jungle of explanatory notes, or spread through different sections of the same document; or the document may not have a table of contents. This makes it difficult to find values you are interested in.

  1. Technical

Many of the parameters involved in road geometric design can be associated with different design approaches, theories and concepts. Some of these approaches and concepts may be out of date, or doubtful, or perhaps not yet widely accepted.


About roadnotes

Robert Bartlett is an international consultant with over 30 years of professional experience as a highway and traffic engineer with leading companies and organisations in several countries, including Germany, China (Hong Kong), Qatar and the UK. Specialised in urban studies, transport and the use of GIS, research has included new ideas on subjects such as the study of social justice using GIS, the dimensions of vehicles, and comparative geometrics (highways and transport).
This entry was posted in comparative geometrics, highway design standards, road design, uncategorized and tagged . Bookmark the permalink.

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