It's one of the most important numbers in the country. Or as John Oliver put it, 911 is the number you call "after WebMD tells you you're not going to be able to get it out on your own."
While your cellphone can post a precise location on Facebook or have a pizza delivered right to your door with no effort, 911 dispatchers often have trouble locating emergency callers.
"Ubers can find you better than ambulances can," Oliver said Sunday night on HBO's "Last Week Tonight."
According to USA Today, the chances of a 911 dispatcher receiving an accurate location from your cellphone range anywhere from 10 percent to 95 percent, depending on where you are. And even if the operators can find you, you can't always reach them because 911 centers are often understaffed and underfunded.
Learn more in the clip above. Then watch an all-too-honest PSA for 911 services featuring Rob Riggle and Wendi McLendon-Covey.