Choosing a route for a short walk
A short walk goes wrong for the same few reasons: the route was longer than it looked on the map, the climb came at the wrong moment, or there was no easy way to cut it short. Choosing well takes five minutes and removes most of those problems.
Start with time, not distance
Distance is a poor guide on hills. A flat five kilometres and a hilly five kilometres are different afternoons. Decide how long you have, then work back: on level ground most people cover about four kilometres an hour, and every hundred metres of climb adds roughly ten minutes.
Write the number down before leaving. It is easier to turn back at the time you decided than to negotiate with yourself halfway up a slope.
Look for a way to shorten it
The best short routes are loops with a shortcut: a lane, a bridleway or a cross path that returns you to the start sooner. On the map, look for a second way down before you commit to the first way up.
If the only way back is the way you came, treat the route as an out-and-back and halve the distance you are willing to cover.