Maybe this can help you:
http://ess.nrcan.gc.ca/pubs/scipub/guide/abbrev/listgen_e.php#H
what highway number is the Golden Gate Bridge
hwy
HWY is the abbreviation used in the US and Canada.
Some states use sthy and others use hwy.
rd.
Hwy
The word highway can be written out fully as Highway or it can also be abbreviated. The abbreviation for highway is hwy.
county highway
Yes, that is correct.
hwy means highway
A state highway is a road that is either numbered by its state with a number that is lower than U. S. national highway routes, or a road that is a U. S. national highway route, but is maintained by the state in which it is located.
There are several state and county roads with that number, and there's Interstate 81.