Petition Category C and D Driving Licence Entitlement

To give those persons who gain a Category C (Rigid Truck) or D (Coach) Driving Licence Entitlement to automatically obtain the other. Both Rigid LGV's and Coaches can be in excess of 18T Gross Vehicle Weight and have similar characteristics (Width, Length, Height and Handling) so why do you have to undertake separate practical tests?. All four modules of the Initial Driver CPC are also very similar - Driver's Hours (Module 1),Case Studies - i.e. Icy Conditions (Module 2), Practical Test (Module 3) and Practical Demonstration Test - i.e. Vehicle Safety (Module 4). Even if you have to undertake Modules 2 and 4 separately for each category why can't you drive a very similar vehicle to the one in which you have demonstrated your professional ability in driving and handling on in order to pass the test for that vehicle?. You develop the same knowledge, skills and experience driving these vehicles so why can't you drive them both after passing your test in one of them?.