The weight of the passengers is a very small part of the whole coach's weight itself, so increasing the capacity of the coach by changing the internal layout doesn't make a big difference for the coach's weight and speed potential as a whole. Each coach weighs less than half the weight of a standard LHB coach, and is a little over half the length of an LHB coach. The decrease in capacity per coach, can be compensated with more number of coaches. There will be some reduction compared to a standard rake, but the difference will be compensated by the reduction in operating costs and higher speed potential.
Also Talgo's higher speed capacity is primarily due to the...
more... shorter coaches, less ground clearance and vestibule design for zero air gap between coaches. All these reasons mean that even with longer rakes, the coaches will still retain a higher speed limit than the LHB coaches on similar track conditions.
The most attractive feature however, is the ability to use all these advantages while spending very less on track upgrades. Signalling upgrades will still have to be made, but usually, the track upgrades and related construction activities are the ones that end up taking several years in our country. Talgo can be quickly brought to service as they are pretty much capable of meeting higher speeds on our existing tracks. If IR doesn't screw it up ( due to politics or whatever), this will be a good bargain for our system.