Not that difficult to isolate a joint, I did one for the gadget shows attempt at the scalextric speed record at chatsworth. They needed an automatic brake section, so I removed the sticking out pin at each side of the joint (just pull with some pliers) and then I shorted the end section so that all cars would brake when they hit that section.
Do it on a joint that is cheap as it is not so easy to fit the pins back.