Traffic calming measures tend to be quite expensive to implement - speed bumps, chicanes et. but here's a way to do it in a much cheaper way. They are truly portable too so that when people get to know where they are they can be moved elsewhere.
One of the worst "traffic calming" areas around here, is in the car-park of our new hospital. The bumps are very steep and narrow - not the "cushion shaped" sort. No matter how slowly you negotiate them, the darned things rattle your teeth! One of them, is positioned immediately at the exit of a tight left turn... it's impossible to hit it squarely, so heaven help anyone who happens to have a painful back or neck! Such good planning... not!