Sounds like a speed camera every 30m would do the trick then.

I'd love to see more of them, but perhaps the penalties should be more flexible to take into account that everyone pushes the limit.

Perhaps as long as drivers do not accumulate too many warnings in a set period then the slate is cleared. Common sense tells us if someone goes down the same route 60 times a month and only marginally breaks the limit once, then they are a safe driver.