Best practice for layered detection in urban canyons?

We are planning detection in a dense downtown area. Multipath is brutal and we get constant false alarms from reflections. Has anyone found a sensor fusion approach that actually reduces them, or is the answer simply more operator filtering?

We are leaning toward radar plus RF with a tighter geofence, but the buildings make line-of-sight almost impossible. Would appreciate real deployments rather than vendor decks.

EDIT: adding a second RF node across the street cut our false positives noticeably. Position diversity helped more than any firmware update.