The train takes 2 minutes to pass through the tunnel. Why? Start a stopwatch as soon as the first part of the train enters the tunnel.
If the tunnel is 1 km long, and the train is travelling at 60 km per hour; it will take the front of the train 1 minute to pass through the tunnel.
To find out how long it takes for all of the train to pass through the tunnel, you need to add the amount of time it would take the back of the train to go through the tunnel as well.
The train is 1 km long, AND the tunnel is 1 km long. When the front of the train leaves the tunnel, the back of the train has just entered. It will take the back of the train 1 minute to travel through the tunnel and come out the other side.
Will Sylvana cry? No.
Each part of the train takes 1 minute to travel the length of the tunnel.
So, if they stay in their seats, Sylvana should only be in the dark tunnel for 1 minute.