Automated Tertiary Road Splitting¶
As part of the September 2019 4.5.6 PMS release a number of tertiary roads were automatically split into two parts - publicly owned and privately owned. This update was undertaken as the OSi removed class 6 and lower roads from the Prime2 roads dataset which resulted in far fewer junctions, leading to long stretches of unbroken geometries.
In total 1,298 automated splits have been created. Galway County new splits are shown below (there are 187 in Galway County alone):
The split locations have been sent to OSi for review, and to possibly implement directly in the Prime2 roads dataset.
Process for Creating Automated Splits¶
The criteria used for automating the splits are as follows:
Find all old edges associated with a single new edge
Check that the old edges were part of a segment at the time of the Prime2 update
Compare the length of the new edge against the length of all the old edges - if it is greater than 50m in difference then it is included in the initial list of edges that may be automatically split.
After this stage 1,633 records were returned - note road class etc. was not filtered at this stage. The next step was to filter the above records with the following criteria:
The collection of old edges must finish with an unattached edge. If nodes at both ends on the old network were connected to segments then they should not be split, such as in the example below. There are 24 of these records that were filtered out.
There must never be 2 splits on the same new edge (like in the example below) - there are 52 roads which would be split at both ends that needed to be excluded, similar to the example below:
Any edges that have user entered PP splits that may be awaiting processing will be ignored so as not to duplicate effort, and give priority to the user entered split rather than an automated one. This was taken into account when deploying to the live server.
All road classes that are not Local Tertiary roads will be excluded. This filters out a further 206 records.
There are several cases where the new edge joins back to the network, whereas in the old network it finished with an orphan node (a node attached to just one edge). E.g.
It does mean there will be splits that end up like the example below - a 51m section that will be marked as private:
The automated splits appear in the Public-Private Splits List, and when deployed will be marked as Processed. The splits are attributed to the superuser account.
