Railway connections play a somewhat lesser role in Greece than in many other European countries, but they too have also been expanded, with new suburban/commuter rail connections, serviced by Proastiakos around Athens, towards its airport, Kiato and Chalkida; around Thessaloniki, towards the cities of Larissa and Edessa; and around Patras. A modern intercity rail connection between Athens and Thessaloniki has also been established, while an upgrade to <answer>double lines</answer> in many parts of the 2,500 km (1,600 mi) network is underway. International railway lines connect Greek cities with the rest of Europe, the Balkans and Turkey.
A current railway upgrade plans to do what?
double lines