There are several speedtraps run on the Northbound NE Extension of 476. The first is between the mid-county exchange and Lansdale. There are a few overpasses they like to hang out just after the bridges.
Another is right at the Quakertown exchange plaza. They will sit in the parking lot.
A third is between Quakerown and Allentown. The best reference location I can give is this:
after Qtown, there is a long hill, as you reach the top, the road will make a long bend to the left, then start turning right. As you come around that right bend, there is an access ramp State Troopers like to sit on.