Severance Snape

This is an experimental tool to study "severances" for people walking. In some places, crossing a big road (a "severance") might be easy -- there's a zebra or signalized crossing right on the "desire line" where someone might want to cross. But often, a person might have to walk a few blocks to reach the nearest crossing -- and then they might have to go up or down stairs to cross on a bridge or a tunnel!

This tool quantifies just how bad this crossing is with a "detour factor" -- the ratio of the length to cross in a straight line and the length of the actual path, according to OSM data. A score close to 1 is great, and a score of 4 means the actual path is 4 times the length of the straight desire line.

This tool is experimental, so there will be bugs both with OSM data and what the tool shows!

To use this tool, you need to:

1. Choose your study area to analyze
2. Check the severances that show up -- they're inferred from OSM data and might not be correct
3. Use the Route mode to explore the detour factor between any two points you choose
4. Use the Score mode to visualize the detour factor everywhere, looking for places easy and hard to cross

This tool aims to complement an "area porosity" analysis, defined in section 2.3.5 of TfL's Cycling Design Standards. That definition of porosity just counts the number of crossings per area, and isn't very detailed about how far you have to walk to a crossing in that area.

This open source tool is created by Dustin Carlino and relies heavily on OpenStreetMap data.