The current system of Driver Licencing, MOT and Tax Classes for large vehicles is confusing not just to those who try to obey it but also those who have to enforce it. Over time alterations have been made and "grandfather rights" left in which cause confusion as to what vehicles can be driven on what licence and what activities are permitted based on Licence held, Tax and MOT classes. A simpler system based on weight with special endorsements for commerical passenger and goods would be a big improvement and make the system much more understandable and regulations easier to enforce for all.
Whilst licencing for Cars is straightfoward, the situation becomes much more complicated when dealing with large Motor Caravans, Horse Boxes, Heritage Buses and Lorries. The situation is complicated further by "grandfather rights" which sometimes extend to the vehicle and sometimes to the driver. Tax and MOT classes in some cases differ from the Licence requirement and each other. For Heritage Buses the situation is further complicated by restrictions on the number of passengers that can be carried in certain circumstances. The situation is so bad that I have on a few occasions contacted the Police, DVLA, DSA and VOSA and had varying responses. As an example I know of one owner of a Heritage Bus who claims he can carry unlimited passengers on his car licence due to having "Grandfather rights" yet when I contacted various authorities about this some told me this was possible and others told me it was not. This included two traffic police who gave different ideas. If those who are supposed to enforce the law do not understand it what hope do any of us have?
I would propose that Driving Licence, MOT and Road Tax classes are based on vehicle weight. The current 3.5t, 7.5t and above would work. Additional Licence endorsements and higher Tax and MOT classes would then be given for Commerical Passenger (PCV) and Commercial Goods (HGV).