Don -
I'm under the impression that there's no such thing in Premiere Pro, short of using a plugin like ReelSmart Motion Blur:
http://www.revisionfx.com/products/rsmb/compatibility/
Sure, you could fake it, and that's been discussed in the past, by using a Gaussian Blur and then animating the parameters, but that's time consuming, and doesn't really look like motion blur.
Joe Bourke
Owner/Creative Director
Bourke Media
http://www.bourkemedia.com