Evacuation Timing & Fuel Calculator (Leave-By Time, Traffic, Range & Supplies)

How it works

drive time = distance ÷ normal speed × traffic factor (1.2 light, 2 heavy, 3.5 gridlock) · stops ≈ 20 min per 3 h · margin = max(3 h, 25% of travel) · leave-by = hours to impact − drive − stops − margin · congested fuel use ≈ normal × 1.2–2 · water 4 L/person/day, 2 L/pet

Evacuation goes wrong in two ways — leaving so late that the road becomes the dangerous place, or running out of fuel in traffic that moves at walking pace — and both are questions of arithmetic done before the pressure arrives. The drive takes a multiple of its normal time once a whole region is on the same highway, stations along the route empty a day or two ahead, and the destination must be reached with hours to spare because roads and bridges close before the worst conditions. Working back from the forecast arrival gives a leave-by time and, before it, a start-packing time; if the sums say it cannot be done, the plan changes to the nearest shelter, not a faster drive.

Worked example

With tropical-storm winds 36 hours out and a 320 km drive normally taking 3.6 hours, heavy evacuation traffic makes it about 7.1 hours plus 40 minutes of stops and a 3-hour margin — 10.8 hours — so you should be on the road within about 25 hours and start preparing within 21. Stop-and-go driving burns about 38 L, more than the 35 L in the tank, so fill up first; four people and a dog need 54 L of water and roughly $700 in cash.

Frequently asked questions