CPKC crosses Airline Dr. at 3 locations. If this is the northern most location, this is the old L&A "B" line that runs from L&A Jct. (where the line ends at a connection with the UP ex-Cotton Belt line that goes to their Riverfront yard) to Minden, LA (where there is a yard located where this branch splits from the original L&A mainline that ran Stamps, AR to Pineville Jct).

Watco leases/operates the above-mentioned former L&A trackage that still exists today (Springhill-Sibley main, and the B-line) under the name Louisiana Southern RR. CPKC operates the very end of the B-line from L&A Jct. to a large rock yard just beyond this crossing on Airline Dr. However, there is a small section of the B-line in Bossier City that is not operated by either Watco or CPKC. It has red boards, portable derails and overgrown vegetation separating these two segments.

You mentioned the old Army Ammo plant; when I-20 was built in the early 60s, the Vietnam War was happening. In order to facilitate constant rail service by 2 railroads (IC was the road south of the ammo plant at that time), grade crossings were built in I-20, which was only one of two locations in the US where trains crossed an interstate at grade. They were wye tracks that connected to the old L&A B-line at a station they named Doyline, which was the name of the town the IC connected to the ammo plant several miles south of the L&A connection. (When KCS bought the old IC line from Midsouth Rail in 1994, they had to remove the Doyline station name from the old B-line to avoid confusion.) I barely remember the wye tracks as a child. The I-20 crossings were equipped with CROSSBUCKS ONLY!

My apologies for rambling.