mutt, g'day
firstly as you will appreciate in godzone country we might and indeed do things differently.
so as a bit of background reading try this
http://www.casa.gov.au/rules/1998casr/139/139m06.pdf
runway width can be a touchy subject and as i've retired and had more than my say on the subject i'll let others have a goanna.
listening out qantas, virgin blue, rex.
best rgds
the "e"
PS if the pdf directs you to another chapter, eg Chapter 13, just delete the 06 bit and type in the chapter number. In passing the runway strip and RESAs are either enlightening or frightening by parts.