For some people it is their full time transportation,others for fun and others use bikes sport. Bikes are kind of taking over the millennium. It has got so big that now cars have to move on over and share the road. Trick bikes for sport and mountain bikes for heavy duty riding. People save a lot of money travelling on bikes.
Bikes can also be kind of dangerous though.
People have suffered bad injuries because of injuries caused by bikes. I use to live in Durham North Carolina where some parts were busier than others. North Carolina also has a lot of big dirt roads and fields of green grass so there was a lot of riding area for anybody to have a good time. There are also a lot of places you can ride here in Philadelphia, almost in every school yard and the great parks of the city. Safety is also a issue with a lot of the youth.