Between 1988 and 1992 British Rail carried out a total route modernisation which included resignalling from Marylebone to Aynho Junction, and both Marylebone to Aylesbury routes, from the new Marylebone Integrated Control Centre. This was combined with track rationalisation that removed most of the vestigial traces of main-line heritage from the line, downgrading it to a purely commuter line with a minimal infrastructure. Until then, much of the four-track section between Northolt Junction and West Ruislip had survived, and High Wycombe station had retained almost all of its original track layout, though the other major stations on the line had already been downgraded with their through lines removed. At the same time, the New North route between Old Oak Common and Northolt Junction was singled between Old Oak Common and Park Royal and between Greenford and Northolt Junction. In 1992, the signal box at Aynho Junction was closed and replaced with modern signalling controlled from Banbury South signal box; the box was demolished in 2002. As part of these renovations, BR installed the advanced Automatic Train Protection (ATP) system, mainly as a trial with a view to rolling it out nationwide. However, privatisation intervened, and the Great Western Main Line was the only other line to be so equipped.