Human reaction time, of course, varies from person to person and tends to drop off in both speed and consistency with age. Significant age related reaction time loss tends to happen in the mid-sixties, though that does not seem to be the case with Jim Boudreau
.
Human reaction to visual stimulus (bulb) averages around .180. It's faster in response to touch (.155) and sound (.140). It's considered impossible for the human to react faster than .100. in modern track and field, it's considered a foul if someone moves faster than .100 from the gun.
I expect it's fair to estimate the human contribution to the overall reaction time (car plus driver) to be about .200.
How to improve it, well, is another story.
Bruce Deveau