What is 4-D barrel racing?

1D is the fastest time at the jackpot. The 2D would be typically 1/2 second slower, and 3D is a 1/2 second slower than that. Usually the jackpot will advertise "1/2 second splits" or "1/2, 1/2, 1" (for a 4D).

Example:

5D barrel race (1/2 second splits)

1D - 15.513

2D - 16.013

3D - 16.513

4D - 17.013

5D - 17.513

4D barrel race (1/2, 1/2, 1 second split)

1D 15.513

2D 16.013

3D 16.513

4D 17.513

I think this is right.