impact of investment expenditure, both in the short and long term. completion of public works while the available data do not enable us to make systematic and detailed comparisons, there is evidence that the average completion times and costs for public works are relatively high in our country. according to the audit performed in 2018 by the european court of auditors, italy has the highest constructions costs of any eu country for completed high - speed rail lines ( €28 million per kilometre, compared with €12 million for spain, €13 million for germany and €15 million see the european spatial planning observation network, espon atlas mapping european territorial structures and dynamics, 2014. see the world economic forum, the global competitiveness report 2017 - 18, geneva, 2018. see the european investment bank, relazione sugli investimenti 2017 / 2018, luxembourg, 2018. see also the chapter ‘ the infrastructural endowment ’, banca d ’ italia, annual report for 2010 ( abridged ), rome, 31 may 2011. for france ). if we add up the costs of projects already completed with those in progress, we find that italy ’ s cost per kilometre rises to €33 million, as against €14 million for spain and €15 million each for germany and france. our country also falls far behind in terms of completion times. 12 surveys conducted over the last decade have shown that, in italy, the average costs per kilometre and completion times for high - speed rail lines have been about three times those of france and spain ; the average costs per kilometre for roads were more than double those of spain. as for major projects co - financed by the european regional development fund, these studies indicated time and cost overruns in italy equal, respectively, to more than triple and double the eu average. 13 it does not seem that the extent of these differences can be explained merely by the distinctive orographic features of each country. the various phases of construction have differing impacts. the length of ‘ transition ’ periods, that is, the time between the end of one procedural phase and the start of the next ( for example, the planning and awarding of contracts ) or between sub - phases ( for example, preliminary, final and executive planning ), has a considerable impact on project timelines. these periods, which are at least in part absorbed by administrative activities and inefficiencies, account for on average around 54 per cent of a project ’ s total duration ( rising to 60 per cent if

, the higher the weight. the figure for risk - weighted assets ( rwa ) represents the sum of these risk - weighted positions. required capital, in turn, is defined as a percentage of rwa. there are two different approaches for setting risk weights. under the standardised approach, risk weights are prescribed for broad asset classes. under the model - based approach, by contrast, banks can use their own internal models to determine the risk weights for different assets. the credibility of rwa based on banks ’ internal models is increasingly being called into question by market participants, analysts and authorities worldwide. it is widely accepted that a bank ’ s risks can, in principle, be more accurately quantified using the model - based approach than using the standardised approach. yet banks ’ internal models are extremely complex and can vary widely between banks, owing to the use of different model choices and model parameters. this can result in different capital requirements for banks with a similar asset structure. this makes it difficult to accurately assess a bank ’ s resilience, and to compare one bank with another. bis central bankers ’ speeches to increase the usefulness and credibility of the model - based approach, in - depth analyses need to be carried out to determine whether and to what extent the model - based approach and the standardised approach lead to differences in rwa. the standardised approach does have shortcomings. yet, since it is independent of bank - specific modelling assumptions, it provides market participants with an additional point of reference for assessing both the level of and changes in model - based rwa. differences between the two approaches must be well explained and have a sound economic rationale. if the analysis does not reveal any substantial inexplicable differences, this will strengthen market confidence in the modelbased approach. otherwise, appropriate measures should be considered. this could, for instance, entail setting a floor for some model - based rwa, such as that recently introduced for banks in the us. another option would be to introduce a multiplier on model - based risk weights for specific positions, as already imposed by finma for some mortgage loans. efforts are underway at finma, supported by the snb, to analyse potential differences between the two approaches. in this context, the snb recommends that the big banks increase transparency with regard to their risks. this includes, among other things, publishing their internal measures of total risk. disclosing rwa according to the standardised approach