The most recent State Route to be decommissioned was State Route 61, which bid farewell upon opening of the Westlink M7 in December 2005. However, remnant State Route 61 signage was not completely removed until mid-2006.

How it works - Allocation of Numbers

The Department of Main Roads provided a good explanation of how numbers are allocated to routes in their 1978 publication Interim Guide to Signs and Markings. This publication was formerly available on the RTA website, however has since been removed. A general rule of thumb that applied to all areas was that no State Route would exist with the same number as a National Route in New South Wales, however this rule was broken with the use of State Route 55 (Natioal Route 55 was the Castlereagh Highway) and later State Routes 31, which was a 'downgraded' National Route, and 44.

For the purposes of allocating route numbers, state routes in New South Wales, excluding the former Freeway Route marking system, were divided into three categories - Sydney area, rural areas, and Newcastle & Wollongong.

Sydney area - The system comprises a ring system of routes carrying odd numbers (21 to 75) and a radial system with even numbers (20 to 76). The lower numbers on the ring routes appear closer to the central city and radial routes are numbered in an anti-clockwise direction from north to south around the central city. One interesting pattern that emerged was that odd numbers with the same two digits (e.g. 11, 33, 55, 77) were allocated to the former Ring Roads (i.e. Ring Road 1 became State Route 11 and so on), and that even numbers with the same two digits (e.g. 22, 44, 66) became major radial routes from the CBD.

Country area - Routes in the country area were viewed as an extension of the Sydney system, with the odd-numbered circumferential routes developing into a system of north-south routes (numbered 77 to 99), and the even-numbered radial routes developing into a system of east-west routes (numbered 78 to 98).

Newcastle and Wollongong - The then provincial cities of Newcastle and Wollongong were allocated their own three-digit route numbers - numbers 120 to 149 for the Newcastle region and numbers 150 to 179 for the Wollongong region - working on the same odd (ring) and even (radial) principle as the Sydney system. It is unusual that so many numbers were allocated, given that only a handful of routes were ever signed in Wollongong and probably two handfuls in the Newcastle region.

These rules were generally adhered to, however some exceptions began appearing as early as 1982 (State Route 60 - located in Wollongong, yet uses a Sydney number). A notable exception is State Route 111, which wasn’t even included in the original allocation of numbers, but was introduced in 1989 to replace the former route of National Route 1. I believe 111 was chosen as the number to continue the ‘Highway 1’ theme.

How it works - Paralleling Routes

A small number of State Routes were introduced as ‘paralleling routes’ - basically they replaced bypass lengths of National Routes and were used to service local traffic along the old alignments. Examples include State Route 44 (paralleling route for National Route 32), State Route 60 (paralleling route for National Route 1 through Wollongong), State Route 83 (paralleling route for National Route through the Central Coast), and State Route 89 (paralleling route for National Route 31 from Liverpool to Berrima). Even the Newcastle region got in on the act with State Route 111, which follows the old alignment of National Route 1 through the Newcastle urban area.

How it works - Unsealed Routes

It was general NAASRA and DMR practice not to sign State Routes (or National Routes) along routes that were ‘substantially gravel surfaced’, with the result that State Route 87 only extended as far north as Hillston until the route was fully sealed through to Cobar and Bourke in 2001.

How it works - Signage

Originally, many routes were signed using topknots so that the Department of Main Roads didn’t need to replace reasonably new signs that were in good condition. Eventually, all route shields were incorporated into directional signs as they were progressively updated - much like what was done with the Metroad system. In addition, new signs installed prior to a route’s official introduction would also be designed with the route shield, only to have it coverplated until the route was introduced.

Trailblazers, in the traditional - cut-out shield - form, were not used on the state route marking system to my knowledge. However, following the introduction of Tourist Drives in the mid 1990s modified trailblazers began appearing, using a standard green rectangle; an upwards arrow; and the State Route and Tourist Drive shields. However, most, if not all, of these signs disappeared by the end of 2004.