Words which are out of date (1) carriageway

Road engineers don’t really know what they are talking about – at least, not when they use words inconsistently, or where the meaning starts to fade away. Take for example the word “carriageway”. Definitions are not consistent, and what some definitions say doesnt really fit the way roads are designed and used today. Here are some definitions:

  1. Carriageway (travelled way): “the portion of the roadway for the movement of vehicles, exclusive of shoulders and auxiliary lanes” (Ref. 1711, Saudi Arabia, 1992 ?)
  1. Carriageway: “That portion of the roadway including the various traffic lanes and auxiliary lanes but excluding shoulders” (Ref. 1979 Ethiopia 2013)
  1. Carriageway: “The section of a street or road that is primarily used by motor vehicles (but may also be used by pedestrians and cyclists)” (Ref. 859 Ireland 2013)
  1. Carriageway : That portion of a road or bridge devoted particularly to the use of vehicles, inclusive of shoulders and auxiliary lanes. Divided roads are considered to have two carriagways. (Ref. 138 New Zealand 2005)
  1. Carriageway: “A carriageway consists of a width of road on which a vehicle is not restricted by any physical barriers or separation to move laterally. A carriageway generally consists of a number of traffic lanes together with any associated shoulder but may be a sole lane in width (for example, a highway off ramp)” (source: Wikipedia, here).

Some notes on the definitions

  • Definitions 1 and 2 do not agreewith definition 4 – for example, either a carriageway does or does not include auxiliary lanes
  • Definition 3 contradicts the first two definitions as these only allow that vehicles use a carriageway (and not, for example, pedestrians)
  • Definition 4 introduces the idea of carriageway and ” physical barriers or separation to move laterally”

Two examples

If we look at two road cross-sections (one from a Bangladesh document and one from a UK document) then we could also add that

  • The Bangladesh cross-section has 4 carriageways – basically this means that it would not be true to say that roads can only have one or two carriageways
  • If we take the Wikipedia text “restricted by any physical barriers or separation to move laterally” then the UK cross-section has three carriageways, as the raised kerbs at the edge of the footpath provide a physical barrier

Bangladesh, Type 1: 11 m carriageway with NMV lanes, 2000 (Ref. 687)

cway 1

And

UK “Local distributor in industrial districts” (Ref: 61, 1973)

cway 2

Comment

A possible replacement term for “carriageway” would be to use the term “zone”, modified by the type of use or traffic, so that

  • The Bangladesh example has 4 zones (2 vehicle zones and 2 NMT zones (NMT = non-motorised transport )
  • The Uk example has 3 zones (2 pedestrian zones and 1 vehicle zone)

References

687 – Bangladesh, RHD standard cross-sections, RHD 2004

61 – UK, Roads in urban areas, Department of the Environment, 1973

1711 – Saudi Arabia, HDM volume 2 book 1.2 design of roadways, Ministry of Communications; 1992 (?)

1979 – Ethiopia, Geometric Design Manual, Ethiopian roads authority, 2013

859 – Ireland, Design manual for urban roads and streets; Department of transport, tourism and sport, 2013

138 – New Zealand, shgdm – glossary of terms, Transit New Zealand, 2005

Advertisements

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 basics, roads and tagged , . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s