It is possible that most of the shot was accomplished in-camera...
But you can certainly add blur in Photoshop by doing selective blurs. This tutorial does a decent job of showing how:
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motion blur with masks at picturecorrect.com
It's also possible that they took the road shot, then superimposed the car on it, adjusted the lighting, added the shadow, and put some blur on the car.
There are so many ways to accomplish anything in post-processing!