Those electric motors also work as generators.
The narration for this video is in Russian, but the car's dash and info system are all in English and we have faith that you will be able to understand what's going on. Electric cars are charged by means other than by plugging them in, something which is very helpful in getting a bit of extra range. But the amount of energy recovered like this isn't going to be dramatic unless your trips involves a lot of steep downhill driving. Although as the video here will show, towing the car behind a truck is also very effective.
It's not exactly practical for everyone, and most truck drivers probably won't help you like this. But in a pinch, it definitely would work.