US 1 ALT leaves Washington Blvd at Hammonds Ferry/Caton and not at Patapsco.
This is confirmed in the HLR. Northbound is quasi posted this way (a TO US 1 shield at the Caton intersection). Southbound is not posted anywhere in Baltimore City.
Also oddly, there are relatively new (and erroneous) US 1 shields on NB Washington Blvd just past Patapsco and again at Barre St well downtown.
