When Conrail came in we Penn men had to qualify all of that trackage in order to mark up on the Oak Island Extra list. The main line viaduct from Constable junction to JC float yard was technically in service for lite engine moves but was out of service for trains. Due to no maintenance for many years it was on the verge of being condemned and with the CNJ main downgraded to a single yard track it had out lived its purpose as a jumpover of the CNJ main line and a quick way into the LV JC float yard. The National Docks Branch was the main route to the Jersey city coal yard. It had now become the interchange for all of the ex LV / CNJ Bayonne and Howland Hook traffic that was prohibited from going west over the CNJ Bay Bridge which was also off limits to Freight trains. The only equipment allowed over the bridge were the Budd cars and 3 car diesel passenger trains until 1978 when they too came off.
The National Docks branch was in service to Johnston Avenue only, as the bridge spanning the projects further east was also condemned due to metal fatigue. There were still a few customers at Johnston Ave and the interlocking signals and power switch were still extant but the switch lined, blocked and spiked for the yard and the signals dark. There was still a pristine semaphore signal with a bright red and white blade by Greenville on the LV main that was approach lit and serving as the distant signal for westbound movements to Upper Bay interlocking but that came down around 1978 or so. I recall boiling up the hill and the curve around sundown one winter evening with a 100 car Pullout seeing a brilliant high green on that semaphore, running a couple of LV GP-18s still in LV paint and thinking it looked like 1959 instead of 1977. The old main line viaduct was a nicely engineered piece of railroad that pointed to the LV's prosperity back in the day. The docks eventually opened back up and became a thru main line again, accessing ex EL Croxton yard and the ex PC River line to Weehawken and beyond. Conrail found out a good deal of the old LV in the terminal area quite useful to them.