Previous changes included the use of aspatial tables to record the additional details about bridges, tunnels and barriers. The first two will be represented as a special occurrence of a Road Segment or Road Node depending on scale. Barriers can be represented as a special occurrence of a Road Node or through an event on a Link.

• It is now proposed that all State Roads will be represented as Links and Carriageways in the initial implementation of the LIST.
• The direction of a Road Segment will only be specified through the direction of the coordinate string if it is supports traffic travel in one direction only. All such Road Segments will be attributed with the type 'O'.
• Carriageways will be derived from Road Segments, however all internal nodes will be downgraded to verticies and they will be assigned a direction through their representative coordinate strings which is that of the associated Link.
• Attributes of road surface, maximum grade, access restrictions, travel restrictions and maintenance authority will now be recorded through chainage tables associated with Links. It is not proposed to compile this information prior to April 1999.
• Road Segment types have been extended to include 'O' for one way and 'P' for private.
• A general road classification system has also been introduced. The codes are included in the RdClass code list.
• Road names other than those for State Roads will now be recorded at the Road Segment level. Where a segment of State Road has a second name (eg High Street) the appropriate Road Segments will also be attributed with the nomenclature registration number for 'High Street'.
• Where a Road Segment or Road Node also represents a Bridge or Tunnel, the link will be the Road Segment ID.
• The model now has the capacity to record turnability at road intersections. This has been achieved through the attribute JuncTurn on each Road Node. This can have the value 'All', 'None' or 'Some'. If it is 'Some' then values as to which pair of Road Segments are joined can be entered into the special table called Junction Turns.
• Bridge and Tunnel tables can also record which Road Segments are connected. This provides for intersections which are at differing levels.

The following original Road Model notes still apply. Where these are in italics they have needed to be modified.

1. Where possible terms in the March 97 draft of the Australian / New Zealand Topographic Data Dictionary have been adopted. These entities are shown in italics.
2. The classes ROAD, LINK and ROUTE can relate to tables of other classes which use a form of dynamic segmentation to record their location. These could be address ranges, bus stops, speed limits, pavement types finished surface, etc. Whilst these chainage related data will relate to a LINK, they will actually be mapped using a new entity called CARRIAGEWAY. This entity is in use by DOT and is required to accommodate the potential for traffic directions to be both forward and reverse, or one or the other.
3. A ROAD SEGMENT is the smallest physical linear feature in the data set. It is the level at which attributes such as data source and quality can be recorded.
4. A LINK is equivalent to that adopted by the Department of Transport. The concept of links could be extended to cover the whole road network to enable users to attach other information through dynamic segmentation. This will also require the establishment of CARRIAGEWAYS.

 

5. Code lists detail the types of features represented by ROAD BRIDGE, ROAD TUNNEL and ROAD BARRIER.

 

6. An ADDRESS POINT equates to a PROPERTY and would be represented by a point offset from the road network. Refer to the Cadastral data model for further details.

 

7. The ROAD SEGMENTS in a CARRIAGEWAY can be determined through spatial overlay.

   

8. If attributes are not shown these details are included in another model.