The first comment/answer is incorrect. You CAN combine two starter sets. I wrote to RealFX Support and they confirmed this. They said: "You can buy two sets, and use all 4 cars at the same time. The cars and handsets pair dynamically every time, and have 1000’s of channels to choose from. However, some of the track parts you would have duplicates of would be wasted (for instance, you would have 2 starting grids), and of course you would have 2 red + 2 yellow cars.

Only with the help of an extension set. So you can't buy two of these tracks and build them into a whole track. The extension sets will probably not be available until the beginning of next year.....