Traditional procurement includes forms of contracts in which substantial risks, such as design, ground conditions and weather, remain with the public sector. The Mott MacDonald study has recorded large optimism bias for projects procured using this method of procurement. This is attributed to the large number of risks excluded from the contractor's price at the contract award stage (e.g. risk of ensuring fit for functional purpose).
There is a wide range of alternative capital procurement options available (e.g. turnkey contracting, or open book pain/gain sharing type contracts) which change the allocation of risk and incentives on contractors. These provide means to reduce optimism bias and should be considered on a case by case basis.