Great post @suesa, alot of good information.
From some sources i can't tell the name of, i know that people who run from the cops also get an amazing adrenaline boost. I've "heard" them say: "It's like we can run alot faster and don't get tired as usually". This explains that the fear to be caught creates adrenaline giving you the feeling that you can keep running forever. However, this is not true since eventually you will run out of breath and have to stop, unless you're someone from the olympics, but then you wouldn't be running from the cops i guess.