Most adults can run at about 7 mph in a short distance. That would be at top speed. If the same person ran a mile it would probably take about 30 to40 minutes depending if they are tired or fully energized. http://wiki.answers.com/Q/How_fast_can_an_average_person_run. it depends for how long but just a couple seconds i would guess around 15mph im pretty sure that if your physically able to run you could run atleast 15mph for a couple of secounds.