The Proastiakós connects Eleftherios Venizelos International Airport to the city of Corinth, 80 km (50 mi) west of Athens, via the central Larissa train station and the port of Piraeus, and is sometimes considered the fourth line of the Athens Metro. The Suburban Rail network currently extends to a length of 120 km (75 mi) and is expected to stretch to 281 km (175 mi) by 2010. The Proastiakos will be extended to Xylokastro west of Athens and Chalkida. The urban and suburban railway system is managed by three different companies; namely ISAP, Attiko Metro (lines 2 & 3) and Proastiakós (line 4).