Now you officially have a problem. The next thing to try is the transmission. You can downshift a gear at a time and use the engine for braking. Lots of people do this with their manual transmission as a matter of habit. It works just as well with an automatic transmission. Drop to a lower gear, wait for your speed to decrease and then drop down another gear. If there's a grassy median, you can drive onto it to aid the process. The surface of the grass and the uneven ground will provide a little resistance to help slow the car.
If you're doing all this and it looks like you're going to run into something before you get the car stopped, then think strategically. Given a choice between running into something solid -- the massive concrete post of a bridge -- and something that will give way -- a chain link fence -- choose the object that will give way. If you can scrub off speed by edging the side of the car against a wall or a guardrail, that's a good idea. Or, if you can drive up a rising embankment, that will also help.
In other words, if you have time to save the car by using something nondestructive like the transmission or an embankment, use it. If you can't save the car, then save yourself. Do whatever you can to avoid injury to yourself by running into something "soft" or scrubbing off the speed. And if that fails, then relax and hope your airbag is in good shape!