Because the salt is so open - many miles in all directions, there isn't much for field of reference, as I am told. RPM and 1/4 mile markers going by quicker is all you have. A friend said he got his car dialed in and was on a great pass. No idea how fast until he glanced at the tach - 9000rpm in top gear with another mile to go. Ran 235 ish that pass.