The client suddenly asks: "add one more stop first." The first reaction should not be "OK," but to quickly check four things.
1. Is there enough time?
The new trip's time: original itinerary, route, buffer.
2. Does it hit a critical node?
Especially: flight, high-speed rail, formal meeting, scheduled appointment.
3. Can the driver continue?
Check: working hours, next booking, cross-city limits.
4. Is the vehicle right?
After adding passengers: enough seats? After adding luggage: enough space?
A simple risk formula
Available Time − Required Time = Buffer
For example: 4 hours 30 minutes left before the flight. Estimate: 1 hour meeting, 1 hour to the airport, 2.5 hours early for an international flight. Required Time = 4.5 hours, Buffer = 0.
That means: in theory just barely enough, in practice high risk. So the dispatcher should tell the client: "We can try, but there's zero buffer." That's completely different from a casual "no problem."