All of us in the L@WS household have been playing Train Conductor which is free for downloading this week. This app is normally $0.99. This is train app is addicting. It starts off pretty simple get your train number to the matching numbered track by swiping your finger to create connections between tracks. The game increases in difficulty as you earn points to unlock new levels. You are challenged to keep up as additional tracks are added, more trains are running, lengths and speeds of trains vary, and track breaks. You have to think quickly and manage your trains to avoid crashing. This is app is great for fun for any train loving kid or adult.
Highly recommended for ages 4 and up. Younger children can play and enjoy routing and crashing trains, but may be frustrated by the pace of play in higher levels. However, there is an in-app game upgrade/add-on called Cute Trains designed for younger children. I have not tested this option personally.