osm-to-railjson

Generating an infrastructure from OpenStreetMap data

Summary

Here are the step involved in osm-to-railjson:

Graph

To create a graph from the OSM nodes and ways, osm4routing is used.

Tracks sections

Create a track section per edge.

Switches and buffer stops

We use the graph topology to deduce the switches and the buffer stops. For example, if a node has only one edge, it must be a buffer stop. But if it has 4 edges, it must be either a cross switch or a double slip switch.

To decide between the last two cases (and in other cases as well), the information of which edges are connected to one another is required. This connection is called a branch. The angle between two edges allows to determine if two edges are linked. If two edges have an angle less then 30°, they are considered linked. In the previous example with 4 edges, if there is 2 branches, it’s a cross switch, but if there is 4 branches, it’s a double slip switch. This method may result in false positive branching when 2 track sections have a small angle but are not actually linked.

Speed sections

Create one speed section or more by reading the maxspeed, maxspeed:forward and maxspeed:backward tags on each edge.

Electrifications

Create an electrification section by reading the voltage tag on each edge.

Operational points

For each relation with the tag public_transport=stop_area, iterate over its node members with the role stop. They will form the parts of the operational points. Then retrieve the main_code, name and uic from the railway:ref, name and uic_ref tags respectively.

The properties name, uic and local_track_name are generated if they are missing from OSM.

Signals

There are two different ways: extraction from OSM or generation from scratch.

Extraction

Create a signal for each OSM node with either the tag railway:signal:main or railway:signal:combined.

Generation

Different types of signals can be generated:

Intersection: signals protecting intersections
BAL: block signalling using BAL (Block Automatique Lumineux)
TVM: block signalling using TVM (Transmission Voie-Machine)

The rules used for generation are:

For intersections:
- Any switches less than 500 meters apart are considered to be part of the same intersection.
- Signals are placed on each track section leading to the intersection, 100 meters ahead of the switch.
For blocks:
- To determine the length of each block, this formula is used:
```
(v² / 2 * a + rt * v) * m
```
  With:
  - v => the speed limit of the track sections.
  - a => the deceleration of the rolling stock (realistic rolling stocks from open data are used).
  - rt => the reaction time of the driver (5 seconds).
  - m => a safety margin (+20%)

Due to an error in the route generations, each signal is forced to have its sibling in the opposite direction. Meaning that all tracks are two-way. We are currently working to fix this bug.

Detectors

One detector is created for each signal, located at exactly the same place.

Routes

The route generation is achieved in two steps. First, determine all the nodes that will make up the graph. These will be all the buffer stops, all the switches and one signal per direction per track section. Then, for each node, travel along every track starting from it, and stop at the first other node you find. This will be all the possible routes from one node. And combining the ones from every nodes will create the graph of all possible routes.