I can put my truck in gear, let the clutch pedal all the way out and it won't move.what would be the probable cause or causes the problem is?

HI @ all, i an innovation project i am just dealing with transportable forklifts which are mounted at the back of a truck (outside). With that position we have a lot of problems because the enourmous weight at the back leads to accidents and has a negative impact on the driving. Moreover the acutal mounting/position is not perfect. Now we thought about improvement possibilties and I am looking for experts in this field. Maybe there are some people who have thought about that problem before and already has a good idea. For example we were thinking about electronic warning systems, e.g. with sensors who could warn the truck driver if the forklift is not 100% mounted, or for example working with cameras? Every contribution is most welcome!!! Maybe you already had an idea how to improve such things of you know somebody!!! Thanks in advance regards carina