quad cab type trucks

Are there any test for safety of children in back seats?

There are no tests specific to trucks, though the NHTSA and IIHS do crash test many SUVs and Pickups. Unfortunately, many pickups are exempt from side impact crash testing, much as they do not have to conform to other safety regulations which apply to passenger cars. Rollovers are also a serious risk with pickups and SUVs.

Small pickup trucks are definitely not kid-friendly. The rear seat in smaller pickups is often too small for many carseats, and those pickups with side-facing rear jump seats cannot accomodate carseats in the rear at all.

Some of the newer full-size, 4-door pickups with large rear seating are much better. Many are now equipped with LATCH and tether anchors, too. I've seen 2001 Silverado Extended Cabs and F-150 Extended Cabs, and both had reasonable room for proper carseat installation.

For more safety links, see:

www.car-safety.org/links.html