This absolutely can be a useful tool for deaf people or others with hearing/speech difficulties.

However, there are already several ways for deaf people to contact 911 without text-to-911

I work in 911 dispatch, probably the most common way I’ve gotten calls from deaf people is through a video really interpreter. The caller is basically on a video call with an interpreter and they relay what’s being said to us. There’s very little delay in communication like there can be when you’re typing back and forth, and usually it works pretty well. There are some situations where it has its issues, if the caller is somewhere dark it can be hard for the interpreter to see what they’re signing, if they don’t have a video-capable device they of course can’t use it at all, and a lot of our deaf callers come from a behavioral health group home place in our county, and some of those callers have a tendency to just kind of walk off-street in the middle of the call, though it’s still kind of useful because the interpreter can at least try to describe what they’re seeing and hearing in the background if the caller didn’t hang up.

Also all 911 centers (in the US at least, I assume it’s probably the same elsewhere in the world) are required to take TTY/TTD calls. The classic example of these is the caller has a device that kind of looks like a typewriter with a little screen and a speaker and microphone they place a phone handset on. They type out their message,the device turns it into a bunch of beeping noises that go out over the phone line like a regular voice call, and the person on the other end’s TTY device (in our case it’s built into our computer phone system) decodes the beeps back into text. Most, if not all cell phones these days also have TTY built into them in the accessibility settings somewhere. There’s some grammar peculiarities because it doesn’t really include punctuation, and some tty users will use ASL gloss, which is a written form of ASL (ASL isn’t totally 1:1 with English, and if you don’t know what you’re looking at ASL gloss reads kind of like that bit from The Office “why waste time say lot word when few word do trick.”) It also allows for hearing or voice carryover, where the caller is able to hear but not speak or vice-versa, so you only need to use TTY for half the conversation and can communicate verbally for the other half. The 2 biggest drawback is that we hear all of these TTY beeps in our headset, and they get pretty annoying really quick, small price to pay though, and generally only one party can be typing at a time, so you have to wait for them to finish before you can reply.

I will say that, at least in my area, TTY is vanishingly rare. In the 6 years I’ve been here, I’d be amazed if we’ve gotten 3 calls from an actual deaf person using TTY, although we did have one mental health patient who used it on his cell phone and used it to just ramble nonsense at us. He had no hearing or speech difficulties, sometimes we were able to get him to talk to us

In either case, if you call from a landline, we get your address just like a regular phone call, with tty from a cell we also get your cellular location like a regular call. Video relay calls from cell phones can get a little funny location wise because of how the call needs to be routed, often it works out that we get a home address they have on file and not their actual current location. With texts the location data often isn’t very good (although we’re implementing some new technologies at my center that improve on it a bit, though it’s still not as reliable as a voice call in some ways)

I posted another comment/rant in this thread with some of my gripes about how people use text to 911 if you haven’t already seen that, and I do want to reiterate that it is a really good option to have available, we can always use more tools in our toolbox, and it can definitely be useful in some circumstances, but it does tend to get misused in some frustrating ways for us.