Monday, 24 September 2012

Mapping pedestrian casualties in London

The Department for Transport publish full data on recorded road casualties on, and I've been playing around with the data a bit recently, partly as a way of learning some new software skills.

The map below (best viewed at full size) is one result, and shows serious and fatal pedestrian casualties in London in 2011 which were the result of collisions with bikes (in red) or cars (in turqouise). Bigger circles represent fatalities and smaller ones serious injuries.

In total there were 980 serious or fatal pedestrian casualties in London in 2011, of which 33 resulted from collisions with bikes (one fatal) and 609 resulted from collisions with cars (38 fatal). The remainder resulted from collisions with motorbikes, goods vehicles, buses and other vehicles, but I didn't show them as I wanted to keep it simple and was mainly interested in comparing cars and bikes.

Techie details: I downloaded the csv data for casualties, accidents and vehicle records for 2011, used R to merge and filter the data, used QGIS to convert the data to a shapefile, and used Tilemill to combine that shapefile with some other layers, apply stylings and export to PNG. Tilemill does some puzzling things like leaving some of the markers brigher than others for no apparent reason, but hopefully that will be ironed out in future versions.


  1. Out of interest, why did you leave out the non-car KSIs?  Doesn't your illustration overstate the relative danger of bicycles? Why not just have bikes v the rest as the simplest? 

    Then (if you can be bothered - I've no idea how complicated it would be) cars v lorries, or whatever permutations you wanted.

  2. I did it this way because I thought it combined simplicity with relevance, as you hear a lot of comment about the threat posed to pedestrians by bikes but relatively little about the category with the greatest threat, cars. I decided against combining cars with all the other non-bike categories as I'm not sure cars are sufficiently similar to motorbikes, HGVs, etc to lump them all together. 

    The best combination of detail and clarity would probably just be a table of numbers showing each category, which I might put up if I can get round to it. 


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