(€1,40), valid on all urban buses and trains, are also valid on Proastiakos trains between Piraeus, SKA, Koropi and Magoula. Higher fares apply for travel to the Airport, between Magoula and Kiato; and between Thessaloniki and Larisa. A one-way ticket from Piraeus or central Athens to the Airport costs €8 (7.9 on line) and a return ticket €16 (15.5 on line). Tickets must be validated on special ticket validation machines on the platform, before boarding the train. Return tickets must be re-validated before boarding a return train. There are no ticket validation machines on the trains. Future plans Addition of new routes and stations to Proastiakos services depends on the progress of a number of OSE infrastructure projects in Attica. The most important projects are: Construction of a three or four-track line between Rouf and SKA stations. Electrification of lines between Piraeus and SKA. Installation of signalling on lines between Piraeus and SKA. Construction of ten passenger platforms and one "through track" at Athens Central station. Construction of new stations at Tavros, Pyrgos Vasilissis, Lykotrypa, and Zevgolatio. As of April 2011, the introduction of new and more frequent services is mainly hindered by limited line capacity between Rouf and SKA, and limited availability of diesel rolling stock for the non-electrified line. Section: Piraeus – S.K.A. A number of new stations and halts are under construction on this line and they shall be served by Proastiakos trains: Athens (Athens Central Railway Station): The station is extended with new platforms to serve future suburban services. Completed as of August 2017. Agioi Anargyroi: New four platform station served by mainline and suburban trains, plus a freight siding. The fast line platforms are already operational and are served by Suburban Railway and Athens-Chalkis trains. The slow lines are under construction. Pyrgos Vasilissis: Is open after the slow lines between Agioi Anargyroi and SKA are operational. Lykotrypa: Is open after the slow lines between Agioi Anargyroi and SKA are operational. Acharnai Railway Center (SKA): The station is partly open since 2011-04-05, extensive work is still required to finish the first phase of the complex. Section: SKA – Koropi - Lavrio The extension to Lavrio will mostly follow the alignment of the old Athens to Lavrio metric gauge line, which closed to passengers in 1957 and to goods in 1962. Most of the old alignment is still intact, and several bridges, all station buildings as well