An unmarked silver Chevy Impala (Williamsport Police) sits on the on ramp from the Market Street bridge facing east with several marked Williamsport police chase vehicles just down the road out of sight until it’s too late to see them and then they have you. the Impala can only be seen once you’re past it or from he west bound side of 180. I believe they are using some sort of laser device there are 2 sensors usually placed on either side of the road when the speed trap is set up. The sensors are small and difficult to see (a tripod witha small box and a small antennae on them about 2 feet high). This is the same device used at the other speed traps on 220.