A route table details the routes between cities in a table! These tables often feature on paper road maps and show the driving distance between cities, which help people plan their trip. I've not seen an interactive version of this. They are still useful to have as a reference.
I have extended the table so you can include used-defined fields, to give the opportunity for making other comparsions. For example, maybe you are using public transport and want to compare transport modes (bus, train, plane) for a route, so you can include the journey times for each of them.
This implementation only shows the values once as the relationships are symmetrical i.e. the distance from New York to Boston is the same distance from Boston to New York! So, the table is deformed to a tiered version to avoid repeating the values for both directions.
You can find the specifications and code in this github repository.