[Emission]

There are so many variables involved, that the only way to get an accurate comparison is with the same driver, on the same "track", on the same day, with the same timing system.

I've heard of road test gear that uses optical sensors to read the pavement. The instruments start counting when you first roll and can track speed. They can also determine exact braking distances as they see the pavement "slow" as brakes are first applied. The "gray area" is between acceleration and braking in a 0-100-0 test. That could be a second lost!