Karangahape Road / Pitt Street area, and one near Upper Symonds Street in Newton. At the southern end, the line would link to a redeveloped station at Mt Eden. Original estimates for the cost of the CRL were at around $1 billion, taking 5–7 years to plan and build. In August 2014 it was announced that the station at Newton had been dropped in favour of an upgraded station at Mt Eden. In 2015, enabling works for CRL construction began. Main works began in 2018. Following completion of the CRL, some trains will no longer terminate at Britomart. Platforms 5 and 1 will be the through platforms, while platforms 2–4 will remain terminating platforms. Eastern tunnel capacity A proposed alternative to the City Rail Link (CRL) to increase capacity was the duplication of the existing eastern Britomart approach tunnel. This would have required a new twin track tunnel approximately 500 metres long to be constructed parallel to the existing twin-track tunnel, resulting in four tracks from Quay Park Junction and retaining Britomart as a terminus. Estimated costs were $150 million to $200 million, with 4–5 years to plan and build. Such a project would have allowed the same capacity increase as the CRL at approximately one sixth to one fifth the cost, but without any of the additional benefits that the two new CRL underground stations or the more direct route to the Western Line will provide. Initially seen as an inferior, but cheaper and more politically acceptable alternative to the CRL tunnel, the duplicate eastern approach also gained favour as a stop gap implementation due to the comparatively short build time. Even if planning had commenced immediately, the CRL might not have become operational until several years after the maximum capacity of the existing corridor was reached. Moreover, while seen as an alternative to the CRL through connection tunnel, the duplicate eastern tunnel would not have precluded it from being built. A feature that came into operation in 2011 in time for the 2011 Rugby World Cup and allowed an increase in capacity of the existing tunnel is 'bi-directional signalling', which allows a train to leave on the same track on which it entered – freeing it from having to cross over other tracks which may not be safely clear of other trains. In 2019, funding was agreed to restore a five-year commuter train trial between Papakura and Hamilton,