Problem is IR focused most in NDLS-Mumbai line & it became fastest stretch of IR. But running train density is lower in NDLS-BRC-Mumbai line. Whereas both NDLS-HWH via Gaya & via Patna line are over saturated, have plenty of old bridges & higher running train density than NDLS-Mumbai line. So in NDLS-Kota stretch average speed of Fast trains is 105-111 kph. Whereas in NDLS-CNB stretch average speed of Fast trains is 95-1101 kph, a whooping 10 kph speed gap. For eg 12952 takes 4 hrs 25 mins in 467 kms NDLS-KOTA stretch @ 106 kph average speed. But 12302 takes 4 hrs 45 mins in 441 km NDLS-CNB stretch @ 93 kph. Guess what, average speed difference is of 13 kph between 12952 & 12302.