Most operations have a pool whether they built one or not. The question is whether it is visible.
Why it matters
Work that has not been scheduled still exists. If it lives in an inbox, on a sticky note or in one dispatcher’s memory, nobody can see how much there is, how old it is, or whether anything is about to breach a promise. A visible pool turns all of that into a number you can act on.
It also protects the route. Without a pool, every new request has to be placed immediately, which means placing it badly — into whichever day has a gap rather than whichever day the stop belongs on.
How you notice it slipping
The oldest item in the pool keeps getting older. Items are placed in the order they arrived rather than by urgency or location. Nobody can say how many jobs are waiting without counting them by hand.
What to do
Work the pool at a fixed time each day, not continuously. Sort by what breaks first — a promise date, a licence requirement, a customer at risk — and place each item where it fits the route, not where there happens to be room.