[talk-au] road widths in australia

[Liz]

just information gathering away from that going-nowhere conversation on main 
talk

(does not deal with any issue concerned with the value of mapping a road 
width, nor how)

After about 1870 roads surveyed to 1 chain width
earlier roads, travelling stock routes, main roads and roads forming shire 
boundaries, wider than one chain, no examples of specification found


2 chains width
(Bundaberg)
Bourbong Street was gazetted two chains wide allowing ample room for two way 
traffic and centre plantings on the road reserve.

(WA)
First constructed in 1927, the reserve for the two-chain-wide Great Northern 
Highway , road no. 8576, 

undated RTA (NSW) material describing a 30m road reserve width, 
www.rta.nsw.gov.au/.../xsections/md.typical_sections_100.pdf


but this document summarising some research gives more useful information
http://www.arrb.com.au/documents/RiskReporter/RiskReporterIssue4.pdf

• Crash rates have been found to decrease with increases
  in total seal width up to widths of 10 to 11 m. The effect
  of adding width to a sealed shoulder or to a lane is
  similar, although, crash risk is likely to increase on wide
  shoulders (> 2.5 m).
• On rural two-lane highways the crash risk reduces
  substantially with increasing lane width up to 3.6 m
  but is likely to increase on wider lanes.
• Lane width has only a small effect on crash rates for
  urban arterial roads within the range of normal lane
  widths (2.75 m to 3.75 m).
• On urban arterial roads the provision for right turning
  vehicles to stand clear of through traffic substantially
  reduces crash risk; the density of access and type of
  abutting development can substantially affect crash risk.
• Guidance typically identifies the benefits from the
  provision of roadside clear zones with a width of up to
  9 m. However, additional benefits can be gained with
  clear zones of up to 13 m and beyond, especially in high
  speed environments.