12629 takes 47 hrs from ypr to nzm , 14 to 15 hrs more than 12649 or rajdhani which take 32 33 hours. Idle rake, yes I feel this train shud be extended to cdg as 22685 is a very lengthy route. 5 hours each way plus 10 hours for maintenance.
12629 runs via ubl bgm mrj pune. The route from pune to nzm via dd mmr doesnt pass thru any station in karnataka. Pune dd mmr all are in maharashtra. So north karnataka doesn't lose anything.
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point linking ubl to nzm going back to gdg bgk sur then pune. Wont help hubli pax . Rather both these trains can meet at pune jn, proceed via bsr , brc to nzm.

[1] 12629/30 highly preferable?? Statistics shows otherwise.... This is peak summer season... All trains run full, even Duronto, which runs falf empty is jam packed. Check out how is the response for 12629/30 during off season. No end-end pax prefer that train.
[2] Right now 12629/30 is crawling. Diverting it through PUNE-KYN-BRC-KOTA won't slow it down, in fact it can be speeded-up.
[3] UBL-GDG-BGK-BJP-SUR is very lengthy route.
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to give connectivity for all districts of Karnataka, some changes to these trains have to be made:
[A] 12649/50 should run daily in the same slot. It's timings are perfect for both SBC and KCG pax.
[B] 22685/86 YPR-CDG-YPR KSK should start from MYS. MYS-ASK-UBL-PUNE-KYN-BRC-KOTA-NZM-CDG. Slip coach from YPR should be attached at ASK. It should be bi-weekly.
[B] 12629/30 should run via YPR-ASK-CTA-BAY-GDG-BGK-BJP-SUR-DD-MMR-BPL-NZM. It should be tri-weekly.
[C] A new 22649/50 KSK should be introduced. It should run on YPR-DMM-RC-GR-SUR-DD-MMR-BPL-NZM (after completion of GR-BIDR line, it should run on GR-BIDR-NED route). It should be bi-weekly.
[D] Now that GR division will be formed in 2 years, a new SF train should be introduced between GR and NZM via SC. This will be shortest, complete Double Electrified route and also help SC get one more SF connectivity to Delhi. It should be tri-weekly.
[E] A new twi-weekly SF Exp from UBL-NZM via PUNE-BRC-KOTA in lieu of 12629/30.

I'm not against wid ur opinion its really viable, but as i said this train it provides connectivity to north.
Now some facts...
The Belgaum infantry depends on this train to reach Jhansi(Babina infantry). I know personally. Getting tickets in goa is a huge task & same for swarna jayanti.
Secondly this train is also a best option for people of Eastern/Weastern U.P. like...
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kanpur,lucknow cz it touches PUNE. All U.P. based trains connecting bangalore are super crawlers & none of them had pantry except 12591 wiz also a super crawler + every one is not equipped enough to pay 2500 bucks for rajdhani etc. & getting tickets in KK is catastrophic.
That is why NZM QUOTA = JHS QUOTA (only for 12629/30)
& i m telling u frankly IR will newer change its route.
Now regarding for 12650. Yes i m rite cz this train arr at YPR is 20:00 with 30 mins of buffer from Karwar so if it gets delayed then they had left for nothing...!!!
I requested change of time of 12650 for people who reside in kankapura, kollegala, hosur its highly unsafe to make onward travel for respective places at middle of night(personal experience) + idle rake standing.
Its so-so chance that IR should think in that way, so its my suggestion.
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well regarding for MYS if they extend 22685/86 then it might would help effectively.
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Time saving issue...
Already there is a plan with IR to construct a by-pass line for Daund(DD). So this train will avoid this rake reversal in near future & YES it will get WAP-7 from PUNE.
Electrification is under progress on MMR-DD line & then they connect it with PUNE. So train will be speedup soon!!!
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There must be a new train required from UBL to NZM i think that would be feasible on ur suggested route.
& GR-NZM train as route suggested by #AnvitJoshi