Formula
Base minutes = (distance ÷ average speed × 60) + (stops × service minutes) + planned waiting. Buffered transit time = base minutes + (drive minutes + service minutes) × buffer rate.
What the result means
The main result is the route duration from departure through completion of the last delivery. Compare it with the usable length of the promised window, including any loading cutoff or driver-hours constraint.
This is a planning estimate. Traffic, mandatory breaks, access restrictions, and time-zone changes should be added separately when they apply.