They sit on the onramp from Ewing Avenue (at the top of the hill in Franklin Lakes) and wait for people to haul down the hill on their way to work. You won’t notice him until you check your rearview mirror and see the cloud of dirt as he peels out to chase you. Since this is right on the Wyckoff/Franklin Lakes border, the cops sometimes sit in pairs (!!) to avoid any technicalities with border disputes.