Stakeholder Consultation, Turin, November 3-4


The Turin consultation ran over a Friday afternoon and a full working Saturday. On the first day there was a series of presentations on the current prototype of the model.  The second day consisted of discussions on a number of aspects of transportation practice and appropriate modeling approaches.

Minor Issues

The general feeling about the prototype was that it was largely valid (with some structural changes as indicated below) but that it needed to be elaborated at lower levels.

Structural Changes

The prototype model presented 3 high-level objects: It was felt that the following high-level objects would be more appropriate:
  1. Unetrans Network: physical network of unmovable assets with respect to which objects can be positioned
  2. Unetrans Assets: objects that are temporarily associated with the network, e.g. signs, construction zones, inter-modal stations
  3. Unetrans Vehicles
  4. Unetrans Processes

Time and versioning

There is a need for transactional updates on an object.  Each feature requires a time associated with lifecycle events: design, construction, in-service, in-database and out-of-service.  Agencies may retire an object when there is a major structural change, such as addition of a lane.  The object may have different versions, such as a more accurate geometric representation, or even a less accurate representation when an alignment is changed.

Linear reference points

The model accommodates point features, but in addition, calibration points used for linear referencing (“reference points” or “landmarks”) need to be explicitly defined.

Scale and accuracy

Users expressed needs at different mapping scales.  At the high end, users indicated that they work with 2-D geometry at ±0.2m, and develop integrated applications where the geometry — not just linear measurement — is critical.  Other users indicated that geometry was desirable but optional.  Accuracy requirements for linear control are ±2m to ±5m over a 1000m stretch, which translates to 0.2–0.5%.

Objects within objects

Bridges are an example of items that need to be treated as objects in their own right.  A bridge has properties such as height and clearance, that need to be captured explicitly.  A road section object may co-exist as a bridge object.

Major Issues

An overriding objective of the model is to unify, but there were two issues on which there were potential divisions.

Logical network or geometric network?

The model references the ArcGIS feature as the basic network object, which integrates geometry and topology.  It was proposed that the model would be better built around a purely logical network (i.e. a connectivity table with no associated coordinates), because a large community of users have no geometric data.  The position of the development team is as follows:

Transport modes

The properties of road nodes and links are so significantly different from those of rail nodes and links (and similarly air and marine networks), that it appears appropriate to build separate models based on different transportation surfaces, with links between multi-modal transfer points.  This is analogous to the Water model's distinction between distribution and collection (sewer) systems.

Technical Contacts

For further information please contact one of the UNETRANS technical team reps (below).


Jennifer Cadkin <>
Ernie Ott <>


Kevin Curtin <>
Mike Goodchild <>
Val Noronha <>