Huge thanks to Carol and to Jonathan for the link to ORBIS. It’s a sort of Google Directions for the ancient world.
I know I’m not the only author to be delighted at the thought of never again having to take a ruler to a map and then multiply the resulting mileage by the speed of an ox cart in order to get characters to the right place in a plausible length of time.
It should be pointed out, though, that travellers outside the Empire may experience a delay of several hundred years while they wait for the arrival of suitable transport to Europe.
Ruth Downie 
Okay, that is so cool. I’m totally with you on the ruler, the map, and the average speed of an African swallow.
I just tested it on a route for which I previously calculated the answer: by trireme from Athens to Ephesus. I figured that on Salaminia, the fastest trireme ever built, it could be done with only a single overnight stop and two long days. Orbis produced 2.4 days for a standard boat on its quickest route.
That all fits very nicely, doesn’t it? Good to know that the measure-and-maths system did work, even if it was rather longwinded.
I did some experimenting with London-to-Rome and liked the way that in June ORBIS will send travellers on a sea route and in January it will send them down the Rhone. (That’s assuming they survive the attempt to reach France, of course.)
Ruth, ORBIS looks like a terrific resource, so many thanks to you and the colleagues who passed the details on to you. I’ll certainly be using it for Aurelia #5!
Glad you like it – I meant to tell you about it at Crimefest, and completely forgot.
If only General Varus had had this tool. Those three legions might still be alive today.
Maybe there should be an option for ‘routes avoiding potential ambush points’!