PSI - Issue 62

Alberto Contardi et al. / Procedia Structural Integrity 62 (2024) 81–88 Contardi A., La Fortezza F./ Structural Integrity Procedia 00 (2019) 000–000

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roads. This is a great economic loss for whole community; this damage is usually calculated assuming an hourly amount (VoT, Value of Time) for every vehicle that should do a longer trip because of the collapsed bridge. A complete analysis, as it is possible to find in literature, should consider a network of road connections, where the collapsed structure is just a branch of the net. When this connection is interrupted, the traffic is redistributed on the other branches, so that the duration of the trip for every traveler of the network is modified. Nevertheless, for our purposes this approach is too complicated and maybe not necessary. When an important road is closed for a short period of time, almost all drivers that should pass on that road will follow the direction from their satellite navigator and choose to pass through the same secondary road. For sake of simplicity, we assume that the users of the secondary road don’t change their habits and keep on trying to travel the same path. The result is that the amount of traffic on the chosen secondary road increases (it is the sum of the ordinary traffic and the past traffic of the closed road) while the impact on all the other roads is null. The following data are taken from the European DG MOVE Handbook on External Costs of Transport and from the Italian Ministerial decree “Linee guida per la valutazione degli investimenti in opere pubbliche nei settori di competenza del Ministero delle infrastrutture e dei trasporti” (Annex 4). The VoT for cars is reported in European table 87; the values for Italy, in € (2016), are the followings:

Table 4. Values of Time (DG MOVE Handbook) in € 2016 /h per person

short distance (< 32 km)

long distance (> 32 km)

commuting-business

personal

commuting-business

personal

12.8

5.9

16.7

5.9

The Italian guidelines indicates the following ranges, that are similar:

Table 5. Values of Time (Italian guidelines) in € 2016 /h per person

Business

Commuting

Other reasons

Urban trips

12-20 20-35

5-10

5-15

Medium and long journeys

10-15

10-25

Since the alternative path usually is longer than the original, the delay costs for one hour are calculated with the following formula (DG MOVE Chapter F.2.8): = −   ∙  ∙ (2) Where: •  is the actual travel time in the original path (before the collapse of the bridge), in hours •   is the travel time in the alternative path (before the collapse of the bridge), in hours • o is the value of travel time •  is the occupancy factor In this study, for motorways, we propose =1.2 and a traffic formed by 80% commuting and business and 20% personal, so the result is =−   ∙ 17.5 € per car . For freight transports, the corresponding table (n. 88) for Italy gives 1.4 € per tonne and 28.1 per driver. Here we consider an average weight of 20 tons and one driver for every heavy goods vehicle, so the cost became = −   ∙ 56.1 € per truck . In the chosen secondary road, the traffic amount increases, so the speed of all the vehicle is reduced. In addition to the costs due to the longer path, the damage of the reduced speed for all the users shall be considered. It is possible to evaluate the congestion costs using the following data, taken from the European DG MOVE Handbook, tables 105 and 106 (Italian values), where the figures are in €-cent/km per vehicle (2016); ‘near capacity’ is related to traffic flow/capacity ratios between 0.8 and 1, ‘congested’ refers to ratios between 1 and 1.2, while ‘over capacity’ is considered when ratio is above 1.2.