60 Second Commercial by Richard60 (renderosity.com)

Above is a link to a video I help make.  At the beginning is a camera pan which is too fast and probably has the stutter effect you are talking about.  The last part of the video has a car driving at 360 MPH (totally unrealistic) the total course for the path of the car was 1.2 miles.  I think the car movement is nice and smooth.  Doing the math for your car, for 30 frames (1 second) @ 60MPH (reasonable speed) then your car could only move 88 feet, or about 2.9 feet per frame.  Even with my super high speeds (360 MPH)  the car only moves 17.5 feet per frame.  The average car is about 20 feet long.  So at your speed the car should be over-lapping itself for about 7 frames.  Even with my speed the car over-laps frame to frame.   

Poser 5, 6, 7, 8, Poser Pro 9 (2012), 10 (2014), 11, 12, 13