Nowadays route planning applications are ubiquitous on smart phones, on embedded or dedicated devices, and on the web. With these applications, you input a destination and a starting point (or the system automatically geolocates your starting point). The system then automatically calculates the optimal route and presents it to you using natural language and/or a map.
I believe that the first route planner on the web was MapQuest (1996), but before that there were definitely offline tools; for all I know there may also have been online tools that predated the web, and were accessible via the dial-up networks of the day (such as CompuServe). What was the first such commercially released route planning software that could be used on a home computer? I know of one myself from 1983, which I'll post as a very tentative answer to my own question, though I suspect there may have been others that predated it.
I understand that the underlying technology is fairly simple; you just need to model cities and junctions as nodes in a graph, and roads as the weighted edges between them, and then run a shortest path algorithm such as Dijkstra's. Everything else is just bells and whistles. So I would not be surprised if simple, proof-of-concept tools appeared very early on as type-in programs in computing books and magazines. But what I'm actually asking about in this question is software that was sold on digital media, or as part of a subscription service to a dial-up network.