I don't have enough info to hand regarding
cost over-runs, but regarding
time, I've seen over the years many a hording by a road project proudly saying 'Completed x months early'- which of course is more easily achieved if you add months to the declared 'completion due' date
. Under-promise; over-deliver.
Construction generally- a big problem in that it encourages over-promising. With competitive tendering and the 'winner' being the one who submits the lowest price suggests a lot of underestimating and under-pricing- the 'unsuccessful' bidders didn't think it could be done for that price!
Stop-start doesn't help either.- who can 'gear up'/ 'stand down'/ offer continuity of 'employment' in that circumstance? Nor does 'cost-cutting' along the way- it can take longer and cost to redesign to save little or nothing.
At least with a building there is scope for repetition floor-by-floor once 'out of the ground', whereas when in or on the ground soil conditions, and what's in it eg pipes and wires can change often over short distances- witness GW electrification and the costs paid in truncation etc eg Oxford, MML, ...
What should/ could 'the rail industry' do to get a better press and the ear of government?