Public Transport Victoria, Victoria Australia

Network-wide laser survey helps Public Transport Victoria to quickly find locations that do not comply with a revised ‘structure gauge’ standard

Business Challenge
Public Transport Victoria (formerly Department of Transport) or PTV is the statutory authority responsible for the rail network across Victoria.

To facilitate the interoperability of infrastructure, the Victorian Rail Industry Operators Group (VRIOG) maintains a ‘structure gauge’ to form a limit upon which no track-side structures may intrude. This ensures that paths required for the safe passage of trains are kept clear along the rail network. The ‘structure gauge’ also varies with the curvature of the line and maximum speeds permitted on each track section. This dynamic envelope defines the limit within which the train can move laterally and vertically along the track.

VRIOG had revised the ‘structure gauge’ envelope and PTV needed to identify which parts of the existing 6,000km network, both rural and metro, encroached on the new ‘structure gauge’.

The traditional method of passing a physical template over the network is time consuming and was considered impractical in this case.

With extensive experience in conducting laser clearance surveys in rail environments, PTV asked Geomatic Technologies (GT) to help.

Services Overview
Working with PTV staff, GT refined a project methodology to deliver a statewide laser-based clearance survey of the rail network. To conduct the survey, GT’s Asset Inspection Mapping System (GT AIMS) was mobilised onto the PTV’s EM100 track recording car as well as on GT’s own hyrail vehicle. GT AIMS facilitates the capture of 360° laser profiles along with a continuous stream of georeferenced digital imagery.

Using the VRIOG ‘structure gauge’, a template modelling the expansion of the tangent track ‘structure gauge’ to accommodate vehicle end throw and centre throw through curves of varying radii was ‘pushed’ through the 3D point cloud. Encroachments found were categorised according to their location (kilometrage) and type (bridge, signal, foliage). The digital imagery was used to establish if any foliage encroachments were due to long grass and could, therefore, be excluded from the analysis.

The final deliverable to PTV comprised of a spatial dataset of laser data and imagery at each encroachment location. The ‘structure gauge’ analysis identified over 2,000 encroachments. The majority of these were from foliage (89%). However, 300 encroachments found were from structures that included platforms (55%), level crossings (22%), signals and signage (16%), and bridges (7%).

Outcomes
GT’s services provided the following outcomes to the client:
–  PTV now had a comprehensive understanding of the network locations where VRIOG’s revised
‘structure gauge’ was not being met and could prioritise work to address encroachments at  these locations.
–  Using GT AIMS, PTV was able to identify encroachments much quicker and in a more cost  effective way than using conventional survey methods.
–  Delays to train operations were minimised as data was collected at ‘line speed’.