Tiny spaces
Build a track where there are at least N (my suggestion for N: 10 - 30) required BLOCKS with significantly reduced driving space on them (such as 1/3 of block is drivable, or there are those tiny "gates" through which you have to drive). Special requirement: The track should be getting harder the faster the driver goes, i.e., going slowly should be very easy.
Required block = block through which the car must drive (in other words, if the track branches somewhere, then only blocks on 1 branch are counted)