I Googled Caseta de Cobro images and found a lot of pictures - but only one really shows pictures of vehicles and tolls as far as my search went. Lots of pics of trucks that crashed into booths. I still submit that a pickup truck and a car means those with single rear wheels on either side of the axle. It would appear that once you add more wheels to an axle you become a truck and are charged the truck rate. There may be those with differing experiences. Maybe someone can get SCT to define "truck" in writing. Personally, I do not consider a pickup to be a truck - which is why they are called pickups. It seems in Mexico they classify a dually as a truck. But I am no authority on any of this. Just seems this is how we have heard it works over the years. Here is a web address with the only toll picture I found that could be clearly seen......
http://www.arietecaborca.com/wp-content/uploads/cache/33040_NpAdvSinglePhoto.jpg
Googling may turn up better pictures.