The Hurstbridge railway line is a commuter rail passenger train service in Melbourne, Australia. It shares tracks with the Mernda railway line until Clifton Hill, then heads in a north-east direction through the cities of Yarra, Darebin and Banyule, and the Shire of Nillumbik. It serves between Flinders Street in the Melbourne central business district through the northern suburbs up to Hurstbridge. The service is part of the Public Transport Victoria metropolitan rail network. Description The Hurstbridge line traverses the rolling landscape of Melbourne's north-eastern suburbs, at times cutting across hills and valleys, resulting in a somewhat winding and undulating track. It includes the only three tunnels on the suburban electrified system, other than the Melbourne City Loop, although none of them are particularly long or deep. The section from Flinders Street station to Victoria Park was built later than the rest of the line, which was originally connected to the suburban system via the now-closed Inner Circle railway line. There is evidence that the line was originally intended to be connected via this route, but geography and existing suburban development made it a problematic situation. The section to Victoria Park runs through two tunnels under a low ridge just east of the city, but most of the rest runs on an embankment that carries the line above numerous main roads and suburban side streets. After Clifton Hill the line roughly parallels the north bank of the Yarra River, cutting across a number of watercourses flowing into the river, and the ridges between them. There is a third tunnel just past Heidelberg station. The line then encounters steeper grades until Eltham, after which it follows the valley of the Diamond Creek, with easier grades but a more winding route, some curves having speed limits as low as . The inner section of the line traverses heavily built-up suburbs, but the suburbia is less dense between Clifton Hill and Greensborough. The outer end of the line is surrounded by paddocks and patches of bush. The line features four of the largest bridges on the suburban network: twin bridges over the Merri Creek, between Clifton Hill and Westgarth station, another on the up side of Darebin station, crossing Darebin Creek, and a wooden trestle bridge across the Diamond Creek just on the up side of Eltham. At in length, this bridge is allegedly the longest curved wooden trestle bridge in use on