In 1931, an English draftsman by the name of Harry Beck, created the now iconic Tube Map. Beck designed a schematic map of the London Underground that prioritized routes and connections over exact geography to address the growing complexity of the city’s subterranean railway system.
A more intuitive subway map
His solution was to create a simplified, schematic map that was more intuitive to passengers by straightening lines and positioning stations equidistantly, regardless of their actual locations. Beck’s map revolutionized transit mapping by introducing an abstract design that used color-coded lines and regular spacing to make navigating the Tube easier for passengers.
An octilinear design for transit routes
Beck’s Tube Map removed the clutter of unnecessary geographic detail and emphasized the locations stations and the structure of the network. Though initially met with skepticism, the map’s user-friendly layout quickly gained popularity.
Beck used what is known as an “octilinear” design, where network lines follow orientations in multiples of 45 degrees for clarity. Beck’s innovative approach not only transformed how people navigated the London Underground, but it also became a blueprint for transit maps worldwide.
Creating a schematic transit map of the world
Inspired by Beck’s work in transit cartography, researchers from the University of Freiburg used data from the crowdsourced OpenStreetMap (OSM) project to explore whether his design principles could be applied automatically to create a map of public transportation systems around the world. The paper, Large-Scale Generation of Transit Maps from OpenStreetMap Data, was recently published in The Cartographic Journal.
The first step was to extract geospatial transit data (sets of stations and transit lines) from OSM data using a SPARQL query on an RDF (Resource Description Framework) database. This step pulled in raw data representing the physical layout of transit networks.
The data was then cleaned up to remove overlapping lines to create what the researchers refer to as a “clean, overlap-free line graph” of just transit lines. The vector transit data was then optimized for map readability.
The data was then converted to three different styles of schematic layout: octilinear (multiples of 45°), geo-octilinear (geographically approximated), or orthoradial.
Challenges in creating a worldwide schematic transit map
The research team tested their automation process on four different types of transit systems: trams, subways, commuter rails, and long-distance trains. Each map was evaluated in terms of scalability, running times, and quality.
While the method was able to generate global transit maps in under two hours for each network type, some challenges remain:
- Memory Consumption: The schematization step, which transforms geographic data into schematic maps, consumes significant computer memory when dealing with large datasets like long-distance rail networks.
- Map Quality: The output map quality varied. In some cases, dense regions with multiple transit lines were challenging to render clearly. Future refinements may focus on preprocessing the input graph to expand dense areas.
- Data Issues: OpenStreetMap data quality posed a challenge. Missing or inconsistently tagged transit lines sometimes resulted in incomplete maps. Additionally, excessive data, such as Taiwan’s high-speed rail network with over 200 individual lines, resulted in maps that were overly complex.
The authors of the study identified some future goals for automatically the creation of worldwide schematic transit maps:
- Improving the method for detecting and preventing line crossings at inappropriate locations.
- Enhancing map readability by better handling areas of high network density.
- Improving labeling and combining different network types into a single map.
- Investigating hierarchical approaches to handle complex, multi-type networks.
- Incorporating user surveys to assess the perceived aesthetic quality and usability of the maps.
Interactive global transit maps
The authors have made both an interactive map and the geospatial data available. Geographical, octilinear, geo-octilinear, and orthoradial versions of each transit system are available for viewing on the LOOM Global Transit Map website. Users can also toggle between bus, tram and light rail networks (commuter versus long distance).
A scalable transit map
The main objective of this study was to see if automating the development of a worldwide schematic transit map was feasible. While there are improvements and future objectives identified by the study, overall the authors concluded that a fully automated global transit map generation is not only possible but also scalable and practical.
The transit map study
Brosi, P., & Bast, H. (2023). Large-Scale Generation of Transit Maps from OpenStreetMap Data. The Cartographic Journal, 1-25. DOI: 10.1080/00087041.2024.2325761.