Okay, this is seriously the coolest thing I’ve seen on the Internet in a really long time. I’ve been using it for Aven, particularly when it comes to estimating how long it would take the army to move. Not only does it calculate times and routes, it can estimate prices, adjust for seasonal variants, give you the shortest versus the cheapest versus the fastest, and (this is so cool) the little thing at the bottom shows when you’ll hit which intermediate landmarks, how long you’re at sea versus on land, etc.
The only impediment to its usefulness for me is that it’s all clearly done height-of-Empire — which is no surprise, that’s when you have the most places to go and the best information about how long it took. But I will still have some fudging to do since a lot of these roads didn’t exist yet at the end of the Republican and the very start of the Principate.