Density cohesion: sweep the block before you leave it

The ping-pong problem

A fleet that always chased the single highest-scoring property could bounce across your whole service area — clear one lot here, drive ten minutes for a slightly better score there, then come back. That burns fuel and time, and it leaves half-finished clusters everywhere.

Density cohesion is the counterweight. It keeps a tractor sweeping the dense block it's already in until that block is done.

Two forces that hold a cluster together

• Same-block override — a candidate within about 15 driving-seconds of the property just finished (measured as real road travel time from that stop) gets a strong preference, so the tractor keeps sweeping the same tight cluster. This stops it from being pulled away by a marginally higher score elsewhere the instant it finishes.
• Close-pair bonus — properties within about 5 driving-minutes of the one just cleared (again, real road travel time from that stop) get a scoring bonus. Adjacent lots and neighboring properties get finished together instead of being revisited on a second trip.

Together these mean the natural behavior is: arrive in a dense area, clear it out methodically, then move on as a unit.

Why it matters

• Fewer wasted kilometers — less cross-town driving between scattered lots.
• Neighbors finished together — a customer's cluster of properties gets done in one sweep, not in fragments across the storm.
• Cleaner progress — blocks go from "in progress" to "done," instead of dozens of half-swept areas.

Balanced against spreading out

Cohesion is deliberately balanced against start-spread and direction control. Fan-out gets the fleet spread across the map at launch; cohesion then makes sure each machine actually finishes the dense area it lands in rather than skimming and drifting. The scoring weights blend both so the fleet spreads and sweeps.