Turnaround time: setting the clock before you start a hike

A turnaround time is the clock time, fixed before the hike starts, at which the party turns back wherever it is. It is worked backwards from the latest acceptable finish: take off the estimated time for the return, then take off a margin for breaks, slow walking and surprises. Set the number at the trailhead, while the group is rested and the route is in view. Deciding it halfway up a slope, when the summit is close, is much harder.

Start from the latest acceptable finish

The starting point is the time by which the group must be back at the trailhead or vehicle. For most day hikes that is the end of useful daylight. The Sun & daylight tool gives sunrise, sunset and civil dusk for a place and date. Civil dusk is the time when the sun is 6° below the horizon. Sunset is calculated with a 90.833° zenith angle, because NOAA assumes 0.833° of atmospheric refraction for sunrise and sunset calculations.

Sunset is the more conservative limit. Civil dusk is later, so it leaves less light for a slow return. Sunset can serve as the finish time, with civil dusk as a check on the plan.

The sunset and remaining daylight guide explains how to turn those times into minutes left on the trail. The solar tool reports times in UTC. Convert them to local time before doing any subtraction, because the clock on the trailhead signboard or on a phone will be local. A finish time that is correct in UTC but read as local time can be hours out.

The latest finish should also move earlier when conditions demand it. A forecast of thunderstorms, a bus or ride that leaves at a fixed time, or a group that cannot walk in the dark all shorten the window. The lightning safety guide covers how storms change the timing of a day.

Estimate the return leg with Naismith’s rule

Naismith’s rule, published by William Naismith in 1892, allows one hour for every 3 miles (5 km) on the map, plus one hour for every 2,000 feet (600 m) of ascent. The metric form uses 5 km and 600 m. The Naismith’s rule guide explains where the numbers come from and how they are used. The Trail time tool applies the same arithmetic to the return leg you enter, with the pace you actually walk at.

The basic rule does not count descent. Langmuir’s corrections add that. On descents of 5° to 12°, subtract 10 minutes for every 300 m of descent. On descents steeper than 12°, add 10 minutes for every 300 m. The tool offers three settings: none, gentle and steep. Choosing a setting means estimating the slope of the descent, so use the contour spacing on the map or your judgement on the ground.

Naismith’s rule describes hikers of reasonable fitness, on typical terrain, in normal conditions. It does not include rest breaks or stops for sightseeing, and it cannot be used for scrambling. In a group, the rule is usually applied to the pace of the slowest member, so that the group stays together. Wikipedia describes the result as a minimum time for a route, which is why a margin is still needed on top of it.

Add a margin you can name

The margin is the time held back for things the estimate leaves out. It usually covers rest breaks, slower walking when people tire, navigation errors, a wrong turn that has to be retraced, and an injury or a lost item that needs attention. The trail time tool models breaks separately, as minutes of rest per hour of moving, so the margin should cover only what is left over.

There is no rule for the size of the margin. The worked example uses 60 minutes, which is a judgement for a short return on familiar ground. A larger margin suits unfamiliar routes, a group with mixed fitness, or a day with a long drive home. Name the number, write it on the plan, and use the same figure every time you apply the method.

Work one return leg through

The example below uses a 7 km return, with 100 m of ascent and 800 m of descent. Civil dusk is 17:40 local time. The clock times are illustrative, chosen to show the arithmetic.

Naismith moving time   = 7 ÷ 5 = 1.4 h = 84 min
ascent allowance       = 100 ÷ 600 h = 0.167 h = 10 min
Naismith total         = 84 + 10 = 94 min
gentle descent         = −(800 ÷ 300) × 10 = −26.7 min
moving time            = 94 − 26.7 = 67.3 min, rounded to 67 min
breaks                 = 67 ÷ 60 × 10 = 11.2 min, rounded to 11 min
return time            = 67 + 11 = 78 min
turnaround             = 17:40 − 78 min − 60 min = 15:22

The turnaround is 15:22. From that time, the group should be walking back, not still heading up, even if the summit looks close. If the return were longer, or the descent steeper, the same steps give a new time. The worked example also shows why descent matters. Without the gentle correction, the return would be 94 minutes before breaks, about 27 minutes more than the corrected figure, and the turnaround would be set earlier than it needs to be.

Stick to the time at the trailhead

Write the turnaround time on the route card or in a note the whole group can see, and say it aloud before leaving. A time agreed in advance is easier to keep than one decided under pressure. Agree what happens when the time arrives, too. The usual rule is that the group turns back as a unit, and that nobody walks on alone to check the summit.

Summit fever is the name for the pattern where the goal grows more important as it gets closer. The usual signs are new reasons to keep going, such as one more ridge, a clear sky at the top, or effort already spent. The turnaround time works because it is set before those reasons appear. Once the time has passed, the question is no longer whether the summit is reachable, but whether the group can be back before dark.

The turnaround applies to the slowest member. The Tobler hiking function guide covers how walking speed changes with slope, which is useful when the route has long climbs. When someone tires, slows or stops, reset the estimate with their pace rather than hoping the others can make up the time. If the reset means the group cannot finish the planned route, shorten the route. A headlamp belongs in every pack whatever the turnaround time, because a return can run late even when the plan is sound. The ten essentials list covers the other items a late return can call for.

Where the method stops

The method uses distance, ascent, descent, pace and breaks. It does not model the ground underfoot, loose rock, snow, river crossings, weather, the group’s fitness or the navigation needed to find the way back. Each of these can make a return much slower than the estimate, and the margin is the only place in the plan that covers them. For scrambling, exposed ground or off-trail travel, the basic rule is not a suitable model, and the time should come from a route guide or from training.

Weather needs its own check. The National Weather Service states that no place outside is safe when thunderstorms are in the area. When thunder is heard, people should move to a substantial building or an enclosed vehicle, and stay there for at least 30 minutes after the last thunder. A storm that arrives late in the day can therefore cut the walking window far more than the arithmetic shows. Read the forecast before setting the time, and check it again on the day.