Coming to reasons of failure (fall of fame) of DQ Deccan Queen
(1) the biggest blow to this train has been imparted by the much shorter (150kms against 190kms by rail) and faster Mumbai-Pune expressway which has taken the traffic away from Mumbai-Pune group of trains.
(2) Saturation of the rail track adds to journey time and fleeing of max paxs to buses/cars.
(3)...
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Availability of a very wide range of car models to suit every budget at a reasonable price. It is economical for a family traveling in AC car rather than going by ac class of IR.
(4) non availability of reservation in train on demand

* It may be interesting to note Deccan queen did 192 kms in just 2:40 hrs when introduced about 9 decades ago making it amongst the faster trains of the world!
* Currently these trains do the journey from a time ranging from 3:15 hrs to 4:10 hrs depending on the number of stoppages and priority accorded to these trains. Their success in the future depends mainly on how much reduction in journey time they can achieve.
* Out of 192 kms of CSTM-Pune stretch, Local trains are also operated on CSTM-Karjat...
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(98kms) & Pune-Karjat (64kms), where speed of non stop long distance trains is severely restricted by suburban trains stopping at each station. Rest of 29km section (Karjat-Panvel) is mostly the famed Bhor ghat section with heaviest gradients on IR network (about 1 in 37), where operating speed of trains are very slow and trains take 45-55 minutes to traverse.
* DQ maintain avg speed of about 60kmph (192km in 3:15 hrs) on above route with 3 intermediate stops on the short run and take lesser time than other SFs with just 1 or 2 stops. This fact indicates the priority it enjoys on its route.

If DQ is run non-stop in the current setup, it can do the journey in about 180 minutes instead of 195 minutes.
A Ray of hope/possibilities for further reduction of journey time of DQ/Mumbai-Pune rail travel.
- Exploiting the existing DQ route to Ultimate limit that IR can do:
(1) Six laning of CSTM-Kalyan (work in progress,)
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Four tracks from Kalyan to Karjat where suburban trains are operated.(third line is being taken up)
(3) Quadrupling of Pune Karjat track where suburban trains are operating.(planned)
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--a- Above measures can help run DQ run at its max permissible speed without any unscheduled stoppages/slowdowns and reduce journey time from current 195 minutes to about 170-175 minutes.
--b- However, a non-stop train may do CSTM-Pune in just about 155-160 minutes.
--c- Use of LHB coaches with 130kmph speed may bring journey time of DQ to about 160-165 minutes and of a nonstop train to about 145-150 minutes
--d- Further, deploying a Tilting train set with peak speed of 160kmph+ may further reduce the time to just about 120-130 minutes (subject to the condition that track is upgraded to gatimaan standards i.e. 160kmph on straighter stretches).

A Ray of hope/possibilities for further reduction of journey time of DQ/Mumbai-Pune rail travel.
Futuristic projects which can revolutionize and popularize Mumbai-Pune rail travel:-
-(1) Doubling & upgradation of Karjat Panvel route (CSTM-Pune 169kms i.e. shorter by about 23kms as compared to current CSTM-Pune 192km route). It will be CSTM-Mankhurd-Vasi-Panvel-Karjat-Pune route and not CSTM-Thane-Vashi-Panvel-Pune route(186kms). (project being taken up)
-1a-In current setup of tracks...
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ICF SF can do the above journey in about 175 minutes
While a nonstop SF may do in about 155-160 minutes
-1b-After construction of dedicated corridors along the route and shifting of all suburban trains on those routes
ICF SF can do the above journey in about 150-155 minutes
While a nonstop SF may do in about 135-145 minutes
Use LHB coach at 130kmph – can do nonstop in about 130-135 minutes
For the track upgraded to Gatimaan standard (160kmph) and use of tilting train sets, time can be further brought down to about 110-120 minutes
(2) Dedicated Semi high speed (200kmph) track (or 350kmph HST may be done if cost permit) with a much shorter and straighter run reducing the distance from 192 to about 150kms (Ahmedabad-Mumbai-Pune Bullet train was planned but Mumbai-Pune section was dropped to contain total project cost).
Semi high speed 200kmph dedicated with trainsets means CSTM-Pune in about 60-85 minutes and
Dedicated 350kmph line (current fastest) means Mumbai to Pune nonstop in about 35-60 minutes
(3) Hyper loop is being mulled between Mumbai & Pune with a travel time of just about 15 minutes
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