I think the initials are likely the official road name.  Note this official county website which writes out "Boulevard" while abbreviating FDR throughout the documents.
https://www.stmaryscountymd.gov/dpw/FDRBoulevard/

If so, I think this would be very much like the example of the JoS. A. Bank.
https://wiki.openstreetmap.org/wiki/Abbreviations