A recent article about 911 calls not showing location data reveals a disturbing trend. Location information that is relayed to emergency call centers from wireless phones has been declining over the past few years, instead of increasing. This report refers specifically to California callers but is technically indicative of what may be happening across the nation. Generally, AT&T and T-Mobile are reducing the reported location of their customers dramatically, while Verizon and Sprint are increasing theirs slowly. Combined, the performance of all networks is still somewhere below 50% which is far less than what the FCC hoped would be achieved by now.
This tells us that the first thought that should come into your mind during a 911 call is to tell your location. You could "register" your cell phone number to a specific address but that has limited usefulness to a mobile society. The California situation points toward the cellular networks as the weak link in the process. Government units have been upgrading their call centers, users have been upgrading their phones, and the wireless carriers claim their are upgrading their networks.
The only variable that comes to mind is that users are using more data than making calls. Are the carriers' abilities to track us slipping by focusing on broadband, or is something else going on? Don't depend on them to save your life. Be aware of where you are, even in the city.