Most of the decisions that go wrong in the hills are not made on the hill at all. They are made in the last hour before the summit, by a tired brain that has already spent its judgement on the climb and is now negotiating with itself. The turnaround time is the simplest tool we know for taking that negotiation off the table. It is a clock time, chosen in advance, at which we turn round wherever we are, summit or no summit. What makes it work is not the number itself but the fact that it was set by the calm version of us, at a kitchen table, with a map and a weather forecast, before the day had any emotional weight.
Why the descent is where the day is decided
Accident statistics from mountain rescue services and from studies of high-altitude climbing agree on one uncomfortable point: a large share of serious incidents happen on the way down, not on the way up. The reasons are ordinary. Descent loads the knees and the attention differently, the light is going, the party is dehydrated and underfed, and the sense of achievement lowers the guard. On a long day the second half is walked by a different, weaker person than the first. A turnaround time exists to protect that person. It guarantees that whatever happens above, the descent starts with daylight, food and energy still in hand.
There is also a mathematical reason. Descent on good paths takes roughly two thirds to three quarters of the ascent time, but on scrambly, loose or snowy ground it can take as long as the climb, sometimes longer. If we reach the top late, the descent does not shrink to fit the remaining daylight. It stays exactly as long as the terrain says it is.
Building the number from the map
The turnaround time is derived, not guessed. We start from the route and apply a walking-speed rule. The classic one, devised by a Scottish mountaineer in the 1890s, allows one hour for every 5 km (3 miles) of horizontal distance plus one hour for every 600 m (2,000 ft) of ascent. A route of 14 km with 1,100 m of climbing therefore comes to roughly 2 hours 50 minutes for the distance plus 1 hour 50 minutes for the height, about 4 hours 40 minutes of moving time. Later refinements adjust for fitness, pack weight and terrain, and most of us find that adding 25 to 50 percent for breaks, photographs, navigation and mud gives a realistic day.
Next we fix the end of usable daylight. Civil twilight at mid-latitudes gives about 30 minutes of workable light after sunset, less in narrow valleys and under forest, and we prefer to plan for being off difficult ground before sunset, not before dark. From that we subtract the full descent time, then a safety margin of at least an hour. What remains is the latest moment we can be at the highest point of the route. If that moment arrives and we are still short of the top, the day is over as a summit day and becomes a walk.
The same arithmetic can be run on weather instead of light. If a front is forecast to arrive at 15:00, the turnaround time is built backwards from the time we need to be below the exposed ridge, not from sunset.
Turnaround places, not just times
A clock time on its own is easy to argue with. A place is harder. We like to pair the time with two or three physical checkpoints: the col at 10:30, the foot of the final ridge at 12:00, the summit by 13:00 at the latest. Each checkpoint is a small, low-drama test. If we are 40 minutes behind at the col, we already know the summit is unlikely, and the decision to turn round has been made gently, in stages, rather than in one painful moment near the top.
Checkpoints also reveal something about the day that the clock cannot. Being late at the col because of a long lunch is different from being late because the path was under wet snow and every step cost double. The first is recoverable by walking on; the second means the descent will be slow too, and the margin needs to grow.
Honouring it on the day
Here is the part that no formula fixes. At the turnaround time the summit is often visible, sometimes twenty minutes away, and every instinct says keep going. Behavioural research on decisions in the outdoors describes this as commitment bias, sometimes called summit fever: the more we have invested, the more we discount the cost of continuing. The countermeasures are practical rather than heroic.
- Say the time out loud before leaving the car, and write it on the map or the back of a hand. A number that has been spoken is harder to quietly revise.
- Agree in advance that anyone in the party can call the turnaround without giving a reason, and that the group turns together.
- Decide what “twenty more minutes” really means: on most routes it means forty, because we also have to come back down those twenty.
- Keep a second objective in reserve, a lower viewpoint or a lake, so that turning round is a choice of destination rather than a loss.
- Treat a broken turnaround time as a near miss worth discussing afterwards, even when nothing went wrong.
When it is right to move the time
A turnaround time is a rule, but it is our rule, and it can be revised for reasons that were foreseen. The honest test is whether the calm planner at the kitchen table would agree. Moving from 13:00 to 13:30 because the forecast has improved, the party is fresh, the ground is dry and the descent is a broad path is defensible. Moving it because the summit looks close is not. Being “almost there” was never one of the inputs to the calculation, and it should not be allowed to become one now.
The one direction in which we revise freely is earlier. Slower snow than expected, a walker with a sore knee, cloud that will hide the descent line: any of these shortens the day, and the earlier the decision the cheaper it is.
A small habit with a long reach
Turnaround times sound like something for big mountains, but they pay off most on ordinary days: the afternoon walk that starts late, the coastal circuit that meets an incoming tide, the forest loop that would be trivial in daylight and thoroughly unpleasant without a headtorch. Once the habit exists, the number takes two minutes to produce and no effort to keep. What it buys is a descent walked with light and strength to spare, and a summit that, when we do reach it, was earned by the plan rather than by luck.