Using Best-Case Traffic
Map tools often show optimistic travel time. Use recent peak-hour averages for safer planning.
How to Estimate Departure Time Correctly
To estimate departure time, do not start with ideal map ETAs. Start with schedule and required arrival window, then work backward with transit and buffer values. This avoids underestimating queue time, terminal walking, and high-traffic risk.
Leave-By Formula
Leave-by time = scheduled departure - buffer - transit - risk margin
- Buffer baseline: 90 min domestic, 180 min international, 45 min train
- Transit: realistic route estimate for your departure window
- Risk margin: 20-60 minutes for bad weather, events, or peak traffic
Common Estimation Mistakes
Ignoring Terminal Distance
Large airports add 10-20 minutes after security. Include walking or shuttle time in your buffer.
No Backup Route
If one route fails, your schedule collapses. Keep one backup transit option before leaving.