Before we venture into the safety of multiple articulated vehicles or super-long goods vehicles, it is important that we understand the term of road train and its concept. As found in wikipedia, A road train is a trucking concept used vastly in remote areas of Argentina, Australia, Mexico, the United States and Canada to move bulky loads efficiently. The term "road train" is most often used in Australia. In the U.S. and Canada the terms "triples," "Turnpike doubles" and "Rocky Mountain doubles" are commonly used for longer combination vehicles (LCV). A road train consists of a relatively conventional tractor unit, but instead of pulling one trailer or semi-trailer, the road train pulls two or more of them. These should not be confused with land trains, which are relatively lightweight vehicles used for moving passengers.
So we back to the question whether is it safe or not? Wait a second, safe to whom? The truck operators or other road users? I believe many people only concerns of their lives and majority of this kind is in fact not the truck operators! Such a pity clarification but well...Thus, let's focus on the safety of road train to other road users who are your family, your friends, your neighbors, yourself and me. It is a very long vehicle and as such, it is very dangerous to overtake. However, road train is only be used in rural areas i.e. less likely found too often on the road. As long as we don't overtake it, our lives will be spared. Not believing me? Try overtake it! Below are some example of the road train photos from compilation work done by cars world blog. Take a look and beware of the road train.
Source: One CRU