The Bristol Bridge Problem



[Written as part of Notebook Blog Month.]

Last year I walked the Bristol Bridge Walk with my brother. This is a 28 mile circuit in the style of Königsberg’s famous bridge problem, where every bridge in Bristol (or more accurately, every footbridge across the Avon) has to be crossed exactly once. It was designed by Thilo Gross, who figured out that Bristol’s bridge problem can be solved, unlike Königsberg’s. At least until they build more bridges and mess it up.

I wrote a Twitter thread on this a while back but thought I’d try an expanded version here. The interesting bit for me is how much of Gross’s work in creating this route was in defining the problem, mapping all the mess of modern Bristol onto a clean mathematical model.

The original Königsberg bridge problem has the following structure, with four land masses and seven bridges:

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