बिहार संपर्क क्रांति : मिथिला पेंटिंग की सुंदरता और तेज रफ्तार - Keshav Singh

Yes ofcourse, GZB WAP-5 are getting old and are less reliable. lol, I have already heard such stupid rumours abt the oldest original ABB P5 being derated to 110 kmph.
On contrary, those locos are still fit and r hauling Gatimaan @160 kmph. 30007 was used in inaugural run. right?
Also, the first loco to enter Mumbai, after ac conversion in WR was 30001.
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also for Bhopal Shatabdi @150Kmph, they are used even today.
Even the old wap6 turned wap4 locos are given more often to sealdah duronto, howrah-ndls/cst duronto.
I dont think so being old makes the loco unreliable until they are actually derated from 130 kmph to 110 Kmph like the GZB P1 which have got derated recently. Otherwise, they too have hauled Rajdhani @130 kmph n were as good as wap4.
GZB P5, be it old or new are always preffered, be it gatimaan, Shatabdi@150 kmph. And also the talgo testing would be done using them as they are expected to get first HOG P5. Even Mued WAP-5 was given to them from BRC, for testing that also failed.
As mentioned by you yourself, SCR restricts WAP-5 for 110 Kmph and SR restricts it for 100 kmph with the Rajdhani trains. Ofcourse, WAP-4 or WAP-7 become clear preferable option. Instead of GZB, which used to give any link according to the availability as mentioned, i.e WAP4/5/7, LGD could provide a fixed link, Which it does nicely. Precisely, GZB is under pressure providing links for NR n East bounds trains.
And there is a big difference in the distance travelled by Jat Rajdhani (577 Km), LKO Shatabdi (512 km), ALD Duronto (632 Km), on one side and that by BCT Rajdhani (1385 Km), HWH Rajdhani (1450 Km), Mas Rajdhani (2175 Km), DBRT Rajdhani (NDLS-BJU 1119 Km) etc on the other side.
For 20 coach JAT Raj n LKO Sht too, WAP-5 is not a fixed link WAP-7 is given as well. Reason, is already discussed. NR gives any link that is available and why not ? Jat Raj is of NR, NDLS JAT sec is fully of NR, then JAT Rajdhani is a short distance train , with enough slack i.e the timetable is not aggressive (110 mps), it is ok if WAP5 is given. If they can give JAT Rajdhani, Even for ASR/BCT Shatabdi, reasons are similar.
It is very likely that even for 18 coach RNC Raj, WAP7 will be made regular, once BCT n AK Rajs start using their own BRC HOG P7. As BBS Raj despite being just 16 coach like MAO Raj, WAP7 was fixed for it.
Same way for 18 coach TVC/ 16 coach MAO Rajdhani, too TKD/BRC P7 might be fixed like that of Pune Duronto.