Currently for 173:
SR 173
[IN THE SOUTHERN CALIFORNIA AREA]
CHAINS ARE REQUIRED ON ALL VEHICLES EXCEPT 4-WHEEL-DRIVE VEHICLES WITH SNOW
TIRES ON ALL 4 WHEELS FROM THE JCT OF SR 189 TO THE JCT OF SR 18
(SAN BERNARDINO CO)
http://www.dot.ca.gov/hq/roadinfo/display.php?page=sr173