In the fall and winter, I use the local high school track for running and biking. Its a 1/4 mile track and it gets boring quick but better than nothing at all.
I used to live in Berlin Germany where its pointless to have a car and riding at night is no big deal. Have lights, will travel.
And I love running in the dark. I feel like I just kind of fade into the night. I use a light from REI called a "Tikka Plus" by Petzel that I really like. And a clip on blinking red bike light for my rear end.