Pulling from side to side

There is a particular stretch of road where I feel a distinct side to side pull when driving. It's like the car is being pulled one way then the other with a frequency of about a half a second. It's quite disconcerting, and my passenger commented on it too, wondering if there was something wrong with the car. I thought that too first time, but it always happens in the same place, so it is something to do with the road surface itself. Thing is, I've driven the same road in several different vehicles and never experienced this except with the Prius. My guess would be the narrower tires are finding their way into uneven ruts in the road that cars with wider tires ride over. Or maybe the road surface is just triggering some resonance frequency in the drive system. I'm wondering if anyone else has experienced anything similar? It's not a pleasant feeling.

(In case anyone is in the area, I'd be very interested to see if you get the same effect. The exact stretch of road is the right lane of the Ventura Fwy (134) heading west around the South Buena Vista St. exit in Burbank CA.)