Reasons for red flag:
1. You cant travel 615km in 7 hrs(Practically impossible).
2. No one likes to sit and travel for that much distance.
3. You are saying that the train will reach Wadi from secunderabad in one n half hour.(Are you going to clear all MMTS and trains or what!)
4....
more... Your train will enter Secunderabad outskirts at 6pm, congestion will be very high at that time.
Changes I recommend:
1. Increase the journey time, make it practically possible to implement.
2. Ensure that your rake consists of Sleeper and AC coaches.
3. Start your train late night(after 10:30pm), so that there wont be crossing with trains like narayanadri, visakha etc on a single line route.
4. Increase stops between guntur and secunderabad, so that train will reach early morning(congestion will be less in secunderabad) and people on GNT- NLDA- SC will be benefitted.