Presently AC local services on Mumbai suburban main line is being operated with just 3 rakes. That translates to a total of 44 services in a day. People won't wait for next AC local, they will travel in whichever is available first. So even at Metro fares, there won't be big patronage. But once there are 10 rakes in service (120-140 services per day), it will be very useful as an AC local service will be available every 10-15 minutes.