प्रयागराज एक्सप्रेस - जो भी हो तुम खुदा की कसम; लाजवाब हो

Well, my explanation was for a freight train only , and ideally, cannot be extended to passenger rakes just like that. The main advantage with python rakes is that in most cases there is absolutely no need for any shunting operations. The front portion detaches and goes on it's wy while the rear portion continues on it's route. This can be even done with just a single long loop line, without blocking the mainline.
Passenger rakes will need much more, as they will not be run with a loco sitting idle in the middle. So they have to be shunted, and this will require a larger yard. I can think of the following problems with your proposal....
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1) Yard construction and maintenance : Most large stations like HWH etc have the pit lines just before the stations at the outer. Now, the outers are always very congested, with trains always being made to wait for clearance. If 8-9 coaches for multiple trains have to be shunted from the pit lines to some yard far away from the station, they will add more to the congestion by blocking the main lines. So, the only option is to have pit lines and maintenance right at the site of the new yard so that rakes need not be moved for long distances.
But the problem is that pit lines and yards require a lot of space, infrastructure and personnel. There isn't anything like a simple passenger yard. They would need all the equipment, pit lines, washing lines, sick lines etc just like any other coaching yard. This requires a lot of space. And space is something that most of our cities don't have anymore. And there needs to be a minimum amount of traffic before the construction of a yard becomes useful.