TPA has a range of location information products which include digitised boundaries. Travel Zones (TZs) are the geographic units of TPA’s data collection, transport modelling and analysis. They are designed to align as much as possible with current Australian Bureau of Statistics (ABS) geographic classification for that year, to allow for comparison of different data sources at standard geographies.
This is a companion discussion topic for the original entry at https://opendata.transport.nsw.gov.au/dataset/travel-zones-1991