The local trains does not have that much delay in Mumbai and they usually run on time, may be you traveled during week ends as the maintenance takes place during that time and some of the trains usually does to run during Saturday and Sunday, when it comes to long distance train you might encounter delays as it is a common thing and there is nothing you can do about that and only Rajdhani Express maintains the correct timing.
Does bullet trains use the same tracks, if that is the case they might arrive late too unless they maintain the same status as Rajdhani .
Usually a 5 mins delay is normal for local trains but trains beyond Virar do have over 20 mins delay and even central line trains. I used to travel by a local train to Virar and it always starts 20 mins late even though it arrives 5-10 mins early on the platform which makes it a 30 mins delay for no reason. The cases with Passenger trains and Express trains are the worst as the delay is in hours. Only Metro trains run in time with a delay of upto 5 mins as they have separate tracks and Bullet trains too have their own tracks.
