Yeah I just did the math and can run 100 meters for an average of 18.00018 mph. I won't be to full speed for ~30 meters so for a top speed I would estimate 20 mph for me.
Now looking at the world record for the 200 meter dash: The man ran at an average speed of 23.29 mph. The 200 meter dash WR is less than twice the time for the 100 meter dash WR, so the 200 meter dash is the best one to use. Now, an olympic 200 meter dash runner can probably run the whole 200 pretty much flat out without getting tired but it still takes time to get to full speed (again ~30 meters). It says on the internet he ran at a top speed of 28 mph and he might be the fastest for top speed so 28-30 mph would be the fastest.