I became fascinated with public transit planning at the beginning of the outreach process for Link Connections. By the time Alternative 3 came out, I was drawing lines all over maps of Capitol Hill, attempting to design a better network. What I soon realized, though, was that I had no reason to believe that my designs were any better that Metro’s alternatives, nor could I defend them against potential objections. So I scrapped those half-finished plans and sought to develop a tool that would allow some semblance of objectively measuring a hypothetical transit network. What I ended up with is an isochrone map generator; you can see an example of what it generates given a 30 minute range starting from Beacon Hill Station.
I suspect isochrone maps can be a useful tool for transit planning. They can help sell a reluctant community on a beneficial restructure. Showing isochrone maps of before and after the restructure provides a visual demonstration that while the specific routes traversing that community may change, the restructure allows more destinations to be reached at more times of day. That is a difficult assertion to communicate with route maps, even ones that show frequency. By generating isochrone maps from a variety of starting points, revisions of a transit network can be objectively compared by calculating a score derived from counting the number of points reachable within some amount of time, weighted by the percentage of the day when those points can be reached. Furthermore, generating isochrone maps can highlight the needs of transit riders unlike ourselves. By tweaking the generator in ways such as halving the walk speed, limiting the walking distance, or prohibiting transfers of a certain length after dark, it can produce maps that emulate the characteristics of other riders. By seeing their view of the transit network, we can evaluate the impact of restructures with less intrusion of our own biases.
I’m surprised King County Metro does not use isochrone maps publicly in its restructuring process. Perhaps there is a lack of tools; other than Mapnificent—which undermines its utility by making simplifying assumptions about transfer timing—I haven’t found others. But perhaps they simply aren’t compelling in practice. To figure that out, I’d like to give the readers, writers, and commenters on this blog an opportunity to make use of the map generator. The articles and comments here contain an abundance of restructuring ideas large and small. I welcome anyone in this community to propose any restructure experiment that they feel would benefit from having isochrone maps generated. I can only process a limited number of requests, so priority will be haphazardly based on personal interest and ease. (Providing modified versions of Metro’s general transit feed specification files makes life easiest, but simple changes like eliminating a route or comparing the regional impact of an existing restructure are fairly simple for me to do.) Nonetheless, I’d encourage erring on the side of putting forth ideas. After all, if isochrone maps can make our arguments more logically grounded and ideas more worthy of actual implementation, finding a way to generate them is time I’d consider well spent.