This brief but very valuable tip comes from the website of the Oakland Rockridge Neighborhood Crime Prevention Council:
Don't Call 911 From Your Cell!!
When you call 911 from a cell phone, the call is routed to the California Highway Patrol! The CHP then has to find out where you are and route the call to your local police or fire dispatcher, which can lose tens of minutes in a critical situation. The Oakland Police Department has an emergency number for use in cell phones:
Program this number into your cell phone and put it on speed dial!
Also remember that other cities have local emergency numbers for cell phone users. Contact the police departments of other cities you visit regularly and put their local emergency numbers into your cell phone contact list as well.
ONLY CALL 911 FROM A LAND LINE!
This should be widely known, but it's not. Pass the information on to anyone you know in Oakland.