Digital maps and routing

What the algorithm optimises.

How routes are chosen

Roads form a graph; the router finds the cheapest path where cost blends distance, speed and live traffic. It optimises what it was told to, which may not be what you want.

Fastest is not safest, quietest or most scenic.
Walking routes may follow roads with no pavement.

Data quality

Maps are edited by people and go stale. Closed roads, private tracks and seasonal fords are common errors, so treat the route as a suggestion in unfamiliar terrain.