The last major change the railways brought about in design was the introduction of the LHB coaches
..and it was a Transfer of Technology (ToT) from Alstom-Germany. Re-designing of coach sub-assemblies and components is continually undertaken by RDSO and design centers of coach Production Units of Indian Railway...
One thing you shuld knw ...only 2.81 crore were alloted for designing in current FY..
SO...
more... THERE IS NO MAJOR changes IN DD COACHES ...