It's not routinely the kind of the thing you find on a traffic stop. Perhaps it's because one who drives a car with 500 pounds of marijuana is not supposed to run a red light (didn't they ever watch The Wire?).
From the New York Times:
Two officers in an unmarked car noticed a white 2010 Dodge Caravan run a red light and make a quick turn without signaling about 4 a.m. Sunday at the intersection of Merrick Boulevard and Farmers Boulevard. The officers, members of the anticrime unit in the 113th Precinct, followed the vehicle and tried to get the driver to pull over. Instead, the driver sped off, leading the officers on a five-block chase, according to the police..
The officers then noticed 10 large black trash bags inside the vehicle, the police said. One of the bags was partly open, and an officer saw green cellophane wrap showing through. At that point, the officers discovered the marijuana, the police said.
The driver, Queens man Clement Hunter, was charged with 50 counts of felony possession, which is rare, police said, since someone has to be caught with more then ten pounds of marijuana to warrant the charge.