I grew up near there in Ambridge and after moving away with my adult job, went back periodically to visit my Mom who still lived there. When my Children were small, I would take them down there for an hour or so to watch trains.
I never parked on the bridge or drove over it. I always parked on the street near the bridge and walked over. There used to be a donut shop 1/4 block away that made it a good spot too. On one visit during the conrail era, the tower operator, apparently, had placed a printed copy of the train lineup for the day under a rock on the trash barrel that was on the bridge then.
I typically shoot stills, so finding a couple of trains waiting to enter the yard was an opportunity. However, I have not been there for years now.