Every government or Railway minister wants to leave a mark of his own and as per his ideology and creates different classes if trains. Lalu wants to prove as a man of masses and so introduced Garib rath and Yuva trains Garib rath coaches have increased length then ICF added side middle berth so increase capacity of 3AC from 64 to 75-81 berths and decreased the fare and run with more coaches 12 sleeper and 4 chair car making 18 coach set. More 3 AC coaches are added indeed to form a full AC train length and reduce fare and also higher speed of 130kmph. As chair car are not comfortable IR quickly realised that travellers are not interested to travel in overnight trains for long distances in chair car they continued with 3AC. So Yuva trains didn't fo forward apart from 2 introduced. Mamata wanted to introduce high...
more... speed trains end to end nonstop and named them as Duronto with different livery. Subsequently IR came up with flexi fare in Rajdhani Duronto and shatabdi to increase revenue. After NDA came to mark their presence they started Humsafar 3AC, Antodaya Non AC GS , Tejas for day inter city. Each of these class have their own advantages ex Godavari Exp rins between Hyd Vskp linking State Capital with tier 1 city in AP state and used to have 6 AC coaches. Then Garib rath was introduced with full 3AC. Duronto was introduced later as cater end to end demand as premium class train.