Case Study 1: A5 road scheme is hampered by legal challenges
The A5 road from Aughnacloy, Co Tyrone, to Londonderry was commissioned in 2007 and would cover 55 miles (88km).
It is the single largest road scheme undertaken in Northern Ireland.
In 2009, when the preferred route was announced, the cost of the project was estimated at £650m-£850m.
Construction was originally intended to commence in 2012, with completion planned in 2018.
The project was brought to the point of construction in August 2012, with a contractor appointed. Delays from that date have been largely due to a succession of legal challenges.
It is now scheduled for completion in 2028 with final costs estimated at £1,100m - £301m (37.7%) over the original budget.
By March this year, £80.3m had already been spent on the project.
Progress on the A5 has stalled on three separate occasions as a result of legal challenge, most recently in December 2017.
DfI indicated it is progressing work to enable a fresh decision on the project to be taken. It has determined that a further public inquiry is necessary.
Works on the first phase of the project could commence in 2020, for completion in 2022. Today's report warns that a further legal challenge is likely.