That wall is on the right side of I-95. It is the bridge abutment for the airport entrance overpass ramp. They don't use radar here because in order to aim it up the road they would have to be out past the abutment. They just wait to jump on cars speeding past the abutment and they never have to wait long. The speed limit here is 55MPH, but every one is going 70/80MPH. I drive this area every day. They are also looking for people who are getting on I-95 south from Island Rd or the Platt bridge (which enter on the right side of the highway) and zipping across to the fast lane. They also sit on the left in a median cross-over about 1/2 mile further south on I-95. This is just before another airport overpass ramp.

My gf passed this trap with me in the car driving 75+ mph and he didn't move, people must drive REALLY fast for that. We were in a pack of cars going well over 80, some over 90. I think this trap is set here because people just getting out of jams drive crazy fast to make up for it.