Using the drag and drop facility, new vehicles can be constructed from existing vehicles quite quickly. However, be sure to check that the articulation angles between units are appropriate for your new vehicle.
If you drop a tractor type unit onto another vehicle of the same type, Autodesk Vehicle Tracking changes its type to Tractor Used As Trailer. Vehicle Tracking then ignores the steering limits of the tractor when the vehicle is driven. It also checks that a coupling exists at the rear of the existing vehicle and at the front of the dropped tractor. In most cases you should not need to make any further changes to the vehicle. However, if it was necessary for Vehicle Tracking to add couplings you might need to edit the coupling details.
To model aircraft being towed with a towbar-type tug, you will need to change the front axle type to Drawbar. You will also need to set a front coupling at the end of the drawbar.
If using the drawbar-less type of tug you should set the articulation limits for the coupling to the maximum nosewheel angle.