You know they are there ahead of time if you have a radar detector. Mahwah police use Ka radar.

Exactly If you use a radar detector, they use Ka band radar. If you get an X band radar, that's being used by the County Police. White crown vic with a green stripe Before you get to the overpass for Macarthur Blvd, slow down. By the time you're at the overpass, it's too late, He'll have you before you can react Especially during the night, it's impossible to see them as the sit far back and the front of their car is black