Editing High-speed rail (section)

====Road-rail parallel layout====
[[File:NIM Baustelle2001 Leidorf Koeschinger Forst.jpg|thumb|A German high-speed line being built along a highway]]

The road-rail parallel layout uses land beside highways for railway lines. Examples include Paris/Lyon and [[Köln–Frankfurt high-speed rail line|Köln–Frankfurt]] in which 15% and 70% of the track runs beside highways, respectively.<ref>{{cite web |url=http://www.jhcrawford.com/energy/interstaterail.html |title=Interstate Rail Proposal |publisher=J.H. Crawford |access-date=17 October 2011 |archive-url=https://web.archive.org/web/20111008204136/http://www.jhcrawford.com/energy/interstaterail.html |archive-date=8 October 2011 |url-status=dead }}</ref> There are [[synergies]] to be achieved from such a setup as noise mitigation measures for the road benefit the railway and vice versa and furthermore less land must be taken through [[expropriation]] as land may have already been acquired for the construction of the other infrastructure. In addition to that, habitats of local wildlife are disrupted only once (by the combined rail/road right of way) instead of at multiple points. However, downsides include the fact that roads usually allow steeper grades and sharper turns than high-speed rail lines and thus co-locating them may not always be suitable. Moreover, both roads and railways often make use of narrow river valleys or mountain passes which do not allow a lot of infrastructure to be sited next to each other.