Crossrail is underground through London. The Overground uses existing rail infrastructure just under direct TFL management so isn't really new. There are a few

Crossrail is underground through London. The Overground uses existing rail infrastructure just under direct TFL management so isn't really new. There are a few new sections but they exist only to join up two lines. DLR is possibly the only real example of new overground trains and partly that is because it follows existing rail lines for quite a distance.