13. For the purpose of these Regulations—
“Part A mobile plant” means mobile plant used to carry out a Part A activity (including such plant which is also used to carry out a Part B or Part C activity);
“Part B mobile plant” means mobile plant used to carry out a Part B activity, not being Part A mobile plant;
“Part C mobile plant” means mobile plant used to carry out a Part C activity, not being Part A mobile plant or Part B mobile plant.