The rail regulator, Office of Rail and Road, publishes annual efficiency and finance assessments of Network Rail. These includes their assessments of Network Rail’s performance in relation to both major enhancement projects and other areas of spend. In their assessment of 2015/16 the ORR noted an ‘enhancements underperformance of £115m’.
These annual assessments can be found here:- http://orr.gov.uk/rail/economic-regulation/regulation-of-network-rail/monitoring-performance/efficiency-and-finance-assessment
This Government has been clear about the affordability and deliverability challenges faced in the current investment programme (Control Period 5 2014-2019). This is why in 2015 Sir Peter Hendy was asked to replan the programme to put it on a more sustainable footing.
Following Sir Peter's review we have revised our approach to major projects. The effective governance the Department has put in place is helping to manage the programme within the fixed funding available.