Toro has some variable speed walk behinds, but I do not know haw fast they can go.
I remember seeing TV commercials for walk behinds that sense how fast you want to go and adjust accordingly,
but I am unsure of the manufacturer....
I have two Toro Time Master mowers. They are 30" and will walk about 4 mph. If you can keep up with one of them for long you are in pretty good shape. They do an awesome job.
