Treadmill running
It is a good idea for anyone who belongs to a gym to mix running on the treadmill with running outside, this is especially so in the winter when it is
just horrible outside.
It's also great for people who are new to running and are self conscious about pounding the streets, you can still work out and build up your confidence
at the same time.
The treadmill is also easier to use because the ground is being pulled underneath your feet and there is no wind resistance.
It can also be used for interval training and speed work, which invariably will help you run better when running outside.
I personally prefer running outside but its not always possible, its a great alternative.