What happens if you get separated from your trekking group during the Mount Rinjani summit climb at night?

Stop where you are, on stable and non-exposed ground, keep your headlamp on, mark your GPS position, and wait for the agreed search response, because wandering in the dark is how a separation becomes an accident. The summit push starts around 2 AM from the Sembalun rim camp, climbs the final steep volcanic scree in darkness, and the file of headlamps can spread over a long distance, so separations happen every season.

Prevention is a briefing, and it happens before anyone leaves the tent. Agree on the walking order, who leads and who sweeps, the next meeting waypoint, departure and turnaround times, and a strict rule that nobody chases another hiker off the path. Every walker needs a working headlamp plus a spare or spare batteries. The park’s own requirements call for groups of at least two with a certified guide, and the guide’s radio links the group to the park information center.

One belief needs correcting, because it is genuinely dangerous. There is no continuous rope handrail up the summit route: the fixed ropes and ladders that are documented on the mountain are on the traverse between Plawangan Sembalun and Segara Anak, not the night summit line, and the guide’s required 10 meters of webbing is carried equipment, not an installed rail. So if you are alone on the summit slope with no lights in view, you are not standing next to a guide rail, you are standing on a steep volcanic slope in the dark.

If separation happens despite all this: stop, find non-exposed stable ground, keep the light visible, mark the position on your offline map or GPS, call or signal if you have any signal, and wait. The guide will notice the count at the next regroup point and backtrack along the agreed trail. Descending an unknown slope to save time is the single worst decision available, because the summit cone’s loose scree makes a night descent far more dangerous than waiting.

We brief this protocol the evening before every summit push, with the regroup points named, because on this mountain the plan you agree at camp is the only one you can execute in the dark.