The line is planned to travel in a long tunnel under built-up areas and to serve the underground Helsinki Airport station, allowing direct access to the airport terminal from long-distance rail services, as well as to free the rail capacity taken up by long-distance traffic in the current main corridor (the Helsinki–Riihimäki railway) for the increasing local commuter traffic. The tunnel would surface at Kerava railway station, and the line would then continue northward to Tampere as either an upgraded Riihimäki–Tampere railway or a brand new parallel line; and eastward to Kouvola using the planned new Itärata railway.
