As a kid, I saw a cheesy b-movie on television sometime between 1978-1980 where the villain (possibly a mad scientist type) had a laser contraption (that I believe looked like a satellite dish on wheels) that when focused on humans turned them to stone.
I remember one scene in particular toward the end where a (white?) van with a number of people in it was speeding away from the laser, down a hill, but when the van was zapped by the laser it went off the road, hit something and stopped. Someone approached the car to see if the people inside were alright and pulled the driver, a blonde woman, up from the wheel to find that her face had turned to a slab of stone (with a blonde wig on it).
Since it was on TV in the late 70s, it could have been a b-movie, a made-for-tv movie or even an episode of a TV show (though I remember it being relatively long) and it could have been filmed anytime in the 70s I would say, based on the style of it.
Any clues would be much appreciated.