[thomas sheehan]

The answer is in the rule book... (coin flip)

Section 2, page 6 of the NHRA 2012 rule book...

LANE CHOICE
In the Full Throttle Top Alcohol Dragster/Funny Car, and Pro Mod
categories, lane choice is determined by elapsed times. The racer
with the better qualifying e.t. gets first-round lane choice, and in
subsequent rounds, lane choice goes to the racer with the lowest
e.t. in the previous round.

In Comp, lane choice is determined by elapsed time. The driver with
the better qualifying position gets first-round lane choice, and in
subsequent rounds, the lane choice goes to the driver with the
lowest elapsed time (in relation to his or her index) from the
previous round (e.t. is calculated off the actual index, not the
contestant’s CIC corrected Index). If there is a tie to the thousandth,
speed is not the determining factor - the first contestant posting the
time will take precedence.

In all other categories, competing drivers are to determine lane
choice by a coin flip or a random-draw lane assignment.