Video here from Malmstrom AFB where they show off the vehicles in more detail, including the inside of the transporter: https://www.youtube.com/watch?v=r5t1h4HSFWg.
"The Safeguards Transport program is so secretive that only three photographs of the unknown number of vehicles have been publicly released."
... here's quite a few hundred more (moving) photographs of them! https://www.youtube.com/watch?v=k8yLYLSzoIw