I like this, it is very nice, I use this technique a lot, but I do it a little differently and the effects are amazing. You are shooting digitally so that makes it easier - your profile says you have a lot of background (congrats!) but no one to set you straight.
Shoot on a faster shutter so you don't blur the motion. Import it into photoshop, cut the guy (and maybe the vehicle) and create a new layer with it. then, apply a filter (filter>blur>motion blur...) and blur the background.
Due to legalities, I cannot show you any of this style of my work but try it and let me know what you think - the results will be impressive.
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