Sometimes a slow shutter speed provides a creative way to convey motion.
For the best results, choose a slow shutter speed, such as 1/30 or 1/40 of a second, and a slow film (ISO 100) or digital ISO equivalent. As the shutter stays open longer, your subject's movement will appear as a blur and give the impression of speed. Use a tripod to steady the camera at that slower shutter speed so the background stays in focus.
I used blurring to contrast my kids' "speeds." In the first image, bottom right, a shutter speed of 1/800 caught my daughter in action, but didn't show the contrast between the two subjects. The slower shutter speed, right, catches her running through the shot while my son stands still, making it a more interesting image.