Fill in the space at the head of the bed with blankets and pillows and the child sleeps in this space while the two adults sleep in the space below. This prevents the parents from rolling on the child, the child from rolling onto his/her front while the truck is moving.
The child sleeps lengthwise in drivers side back corner, the taller adult sleeps next to the child and the shorter adult sleeps beneath the child. Please note, this only works if one adult is shorter than the other. While the truck is moving the child stays in its position with the off duty adult sleeps protecting it.
Two parents in bed and baby on the floor. The child is place between two evenly sized pillows covered with a pillow. This works for younger babies that do not move a lot and great for parents that toss and turn. Be very aware though if you have lowly positioned air vents because they can give the child a chill. If you must use this position then tilt any vents upward away from the child and cover him up with a blanket.
Just like in option two, the child and first adult share the same positions. However, the first adult curls their knees up so that the other adult can sleep curled up at the end of the bed. This is great for a driver coming to take a nap after a shift and for people that sleep scrunched up or diagonal.
For a while, we put our baby in one of the lower cabinets. We took off the door, padded it down on the inside and he would sleep in there. It was very safe, and quiet in there, and kept the noise and lights down when James and I were up. However, he quickly outgrew the cabinet and we had to move him out on to the open floor of the truck.
The first adult sleeps up against the wall while the child sleeps on the outer rim of the bed. The other adult will need to stay up, however during feeding the second adult can hold the child, face the opposite direction of the first adult in bed while relaxing and keeping warm under the blankets if need be. This is great for an adult waiting to unload or staying up for time off, particularly in colder climates. It is not the safest position for the child while the truck is moving