Which way will you choose?

A mom advised his son not to play around at the railway train road, unless it is unused railway train. So his son always plays around at unused railway train road.

Now this incident happens –

You are the train driver. The train is going to break down and you need to choose a way to slow down your train and stop it. Now, you have to select one of this two railway roads – Current track or unused track.

Unfortunately, children are playing at that moment. The child who had listened to his mom is playing at the unused railway track, while a group of children is playing at current railway track.

Which track will you choose to slow down your train?