Found it! Google Maps walking directions from 38 Cameron Avenue, Cambridge to 38 Cameron Avenue, Somerville: https://www.google.com/maps/dir/38+Cameron+Avenue,

Found it! Google Maps walking directions from 38 Cameron Avenue, Cambridge to 38 Cameron Avenue, Somerville: https://www.google.com/maps/dir/38+Cameron+Avenue,+Cambridge,+MA/38+Cameron+Ave,+Somerville,+MA+02144/@42.3990736,-71.1303421,17z/data=!3m1!4b1!4m13!4m12!1m5!1m1!1s0x89e3771c6d03b453:0x56bbc210b2076366!2m2!1d-71.1288362!2d42.3983958!1m5!1m1!1s0x89e3771c390b68e7:0x9b1f4243ea4952d8!2m2!1d-71.1274405!2d42.3996922 https://www.google.com/maps/dir/38+Cameron+Avenue,+Cambridge... If you zoom in it looks like both cities start numbering from 1 at the "beginning" of the street with numbers going up until they reach the city line.