Well, I finally found a field wide enough to pan an Acela as it sped by at roughly 135 MPH, just east of North Brunswick, NJ. Up until this date the close confines of the city risks twisting one's neck trying to pan left to right as it sped by at close range. After a few attempts at 1/6th I thought I lost my touch but then I realized just how far through the arc of a pan an Acela goes in 1/6th of a second! Consequently, I adjusted my settings and caught a sharp pan at 1/50th.
Enjoy!
ACELA at speed
/Mitch