The Three-Light Trip Plan

Light and time for a caving trip: your lamp read in watt-hours, the trip budgeted mode by mode, two backups that each get you out, a turnaround by half time, and a callout card someone on the surface holds

DeepCave's Headlamp Runtime Calculator takes one power draw for a whole trip, and its Trip Planning Reference sizes spare batteries for one representative lamp on one mode. A real trip mixes modes, every caver's lamp is different, and a backup light only counts if it can get you out on its own. Until this month our own Gear Checklist Generator listed one backup light each and one spare battery set for every two people, however long the trip; it now follows the three-light rule and sizes spares from the trip. The Three-Light Trip Plan carries those tools through. It reads your lamp in usable watt-hours and checks it with a timed run at home, budgets the trip mode by mode with spare sets for it twice over (an example 6-hour trip with one hour on high needs 3 spare sets where the same hours on general need 2), sizes two backups against the way out from your turnaround, sets the turnaround by half time, and turns the exit and callout times into a card someone on the surface holds. Every figure is computed by the site's own code, and the lamps, cells, trips and times are examples for you to replace. It is not caving instruction: it says nothing about rope or vertical caving, which is learned in person with a club, and nothing about air beyond this: if it feels wrong, leave. Inside: seven steps, four printable working pages (light budget sheet, callout card, party kit sheet, after-trip log), reference tables, a quickstart, and a personalised sheet worked from the numbers you entered in our calculators.

Look inside

Two full pages from the plan, exactly as printed. Click either to read it at full size before you decide.

What is in it

• The Watt-Hour Rule: your lamp's usable watt-hours per set, checked with a timed run at home
• The Mode Budget Rule: the trip budgeted by low, general and high mode, with spare sets for it twice over
• The Three-Light Rule: two backups on their own power, each sized to run the way out twice over
• The Own Light Rule: every caver's spares from their own budget, and a light-failure drill
• The Half Time Rule: a turnaround set before you go in, the reasons to turn early, and the forecast
• The Surface Rule: a written callout card, what your contact does at the callout time, and the call when you are out
• The Stop Rule: water, food, a spare layer and the shelter for a trip that has stopped
• Four printable working pages: light budget sheet, callout card (two copies), party kit sheet, after-trip log
• Reference tables: spare sets by trip length and average draw, usable watt-hours and hours by cell
• A quickstart checklist and a personalised sheet worked from your own calculator inputs

The plan picks up where the free Headlamp Runtime Calculator leaves off. That calculator takes one power draw for the whole trip; the Trip Planning Reference sizes spare batteries for one representative lamp; and the Gear Checklist Generator lists three lights, water and food for the hours. The plan carries them through: your own lamp read in watt-hours and checked with a timed run, the trip budgeted mode by mode with spares for it twice over, two backups sized against the way out, a turnaround by half time, and a callout card someone on the surface holds. Every figure in it is an example for you to replace. It says nothing about rope or vertical caving, which is learned in person with a club, and nothing about air beyond this: if it feels wrong, leave.