Most routing software was built for packages. A package route has one constraint that matters: distance. Put the stops in the order that drives the fewest miles and you are done. A vacuum truck has that constraint and three more, and the three more are the ones that make a "shortest route" plan useless by two in the afternoon.
The four constraints
The tank. Every service pulls waste into a tank with a fixed capacity. Somewhere in the day the truck is full and has to go to a disposal site, and the stops after the dump are a different route from the stops before it. A planner that does not know the tank size plans a day that cannot be driven.
Disposal site hours. The treatment plant takes trucks until four. If the plan has the dump at 4:40 the driver either dumps early, with half a tank, and loses an hour, or finishes tomorrow with a full truck in the yard overnight.
Service windows. The school wants the unit done before 7:30. The restaurant does not want a vacuum truck in the lot at lunch. The event has a gate that opens at ten. These are not preferences; they are stops the driver cannot do at the wrong time.
Shift hours and what the truck carries. An eight-hour driver, a truck that carries the units for the delivery at stop six, a disposal site that only takes septage and not grease. The plan has to know all of it or it will put a grease trap on a truck that cannot dump it.
What "around the tank" looks like in practice
Take a truck with a 1,500-gallon waste tank and thirty stops in a county. A distance-only plan sequences them geographically and leaves the dump to the driver. A tank-aware plan tracks the expected pull at each stop, sees the tank crossing full around stop eighteen, and inserts the dump before it. It picks the disposal site that is open at that hour and nearest to stop eighteen, not nearest to the yard. Then it re-sequences stops nineteen to thirty from the disposal site's location, because the truck is starting a new leg from there.
The expected pull per stop is the detail that separates a real planner from a demo. A fixed "40 gallons per service" guess is wrong for a construction unit on Monday and wrong for an event unit on Friday. The planner should learn the number from what drivers actually record on your own routes, per unit type and per customer.
Where the truck starts
A surprising number of bad routes start in the wrong place. The company has two yards; the plan starts every truck at the first one. The truck is parked at the driver's house; the plan starts it at the yard. Each truck should carry its own start and end location, which beats a planner's default, and a company with more than one yard needs every truck tied to its own. The sidebar's list of facilities is not the same thing as the depot a route planner reads, and when they get confused the route starts from the middle of the stops.
Locked stops and the dispatcher's hand
A plan is a draft until a dispatcher looks at it. The two things a dispatcher needs are the ability to lock a stop (this one is at 7:30 and that is not negotiable) and to move a stop to another truck and have the rest re-sequence around it. A planner that re-optimizes everything the moment one stop moves is as useless as one that cannot move a stop at all.
What to test
- Plan your real Tuesday, every truck, with the disposal site hours entered. Does the dump appear on its own, and before the tank is full?
- Move one stop to another truck. What happened to the two routes?
- Lock a morning stop and re-plan. Did it stay?
- Ask where each truck started. Was it right?
If you are comparing tools, the demo questions include these. And once the plan is right, the number that moves is stops per driver per day.
