Children love to race. However, racing indoors can be tricky especially with toddlers who can still be rather haphazard while moving quickly. One way to race safely indoors is to race objects. When we race objects, we contain them in foam pipe insulation since it is inexpensive, easy to find, and easy to store.
To start buy a six foot length of insulation and cut it in half length-wise. Now you have two tracks. If you are feeling creative, you can use cardboard and tape to create curves and hills but it is perfectly acceptable to use straight track as well. Once your track is ready, you can roll a number of things down the track including marbles, small cars, and bouncy balls.
P.S. cardboard makes excellent starting gates.