Modelling intermodal re-balance and integration: planning a sub-lagoon tube
for Venezia
Vincenzo Punzo 1, Vincenzo Torrieri1, Maria Teresa Borzacchiello1,
Biagio Ciuffo1, Peter Nijkamp 2
Abstract
The increasing need, in the transportation sector, for new policy initiatives that generate
positive and sustainable environmental, social and economic impacts is increasingly directed
towards the promotion of intermodal integration in transportation that may prompt a rebalance in the mobility pattern in relevant areas, especially in an urban environment.
An interesting example of a city with a great variety of such complex transportation
challenges is the Venice area in Italy.
In this paper a feasibility study for a sub-lagoon tube connection between Venice island andits mainland is presented. This project aims to improve accessibility and sustainability in the
Venice region, by favouring an intermodal re-balance in the local transportation system. In
particular, the methodology of transportation evaluation and of scenario simulations will behighlighted, while the main results of the study will be presented and discussed. Multicriteria analysis is used here inter alia as an important assessment and evaluation method.
The case study of Venice can be considered as an illustrative study, in which a novel andchallenging urban plan is followed by specific studies assessing the overall sustainability ofthe proposed policy intervention, even though it is not ensued by an immediate
implementation.

Keywords: modal integration, cost-benefit analysis, environmental sustainability, re-balance

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1

Department of Transportation Engineering – University of Napoli “Federico II”. Via Claudio, 21, 80125 – Napoli,
Italy. E-mail: vinpunzo@unina.it, torrieri@unina.it, mborzacchiello@unina.it, bciuffo@unina.it,
2
Department of Spatial Economics – VU University. De Boelelaan 1105, 1081 HV Amsterdam. The Netherlands.
E-mail: pnijkamp@feweb.vu.nl

Integrated and intermodal transport: a matter of sustainability
The debate on sustainable development is already more than two decades old. It has focussed
in more recent years in particular on sustainability governance, especially from a regional (local)
and/or domain (sector) perspective. Transportation is one of the prominent sectors often addressedin this context. And policy-makers are desperately seeking for solutions to cope with thesustainability challenges related to modern transport and mobility.
Transport is one of the world’s largest industries and in many countries it accounts for up to 20
per cent of the nation’s gross domestic product. There is, however, a cost associated with thisevolution of transport. The history of motorized transport is one of large-scale environmental
intrusion and in many respects it is becoming even more harmful with its extensive use of fossil fuel.
Transport poses many operational and logistic policy problems, but the environmental implicationsof the motor car, trucks, aircraft and the like are indeed very challenging (Banister and Button, 1993;
Button and Nijkamp, 1997; Button and Stough, 1998; Button et al., 1996). The projected trend ingrowth in motorized land-based traffic, aviation and shipping into the new century means thatcurrent policies will at least need refining to cope with the situation.
Transport is also often demanded in close proximity to where people live, work and spend
their leisure time. Indeed, it is the very access afforded by transport that permits the modern lifestyle
we find in the developed world (Button and Nijkamp, 1997). This again poses many more problems
when contrasted with other major sources of environmental damage. In developed countries,
populations find limited incentive to use less environmentally intrusive modes of transport and policy
makers are finding it difficult to obtain anything but minimum intermodal shifts from the use of the
motor car and from trucking. The car affords a number of private benefits over public transport. In
practice, the lure of the motor car is much stronger than most transport forecasting models predict
and many efforts to foster more environmentally-benign public transport use ignore the massive
quality differences involved in getting straight into a car at one’s home after being able to choose
exactly when to leave the house, adjusting the temperature to that desired, listening to music that
one likes in one’s own company or company of one’s choosing, being able to carry large packages
conveniently in security, to select alternative routes periodically to avoid boredom, sitting in seatsthat have been selected from the wide range that are available in different vehicles and so on. Public
transport does offer an attractive variation on dry days when the timing is convenient and one has
little to carry but in most cases there are major differences in service quality. Getting people toswitch to public transport requires sticks as well as carrots (see Banister et al., 2000). Integrated
transport policy is indeed a major challenge.
At the micro level, where environmental concerns with noise, fumes and the like have more
traditionally been focused, there is also the issue that while some policies have proved to be very
successful, many problems still remain or have been created. Lead, for example, has been removed
from gasoline in many countries but, for combustion reasons, many types of fuel now containcocktails of aromatics that have other potentially harmful effects. Equally, the adoption of the ‘zero
emissions cars’ policy in California may introduce a small number of electric cars into the system, but

1

of itself it simply moves the location of much of the pollution from the streets to other power
generation sites.
Technological policies are direct and consist of measures that make the vehicle orinfrastructure more environmentally benign. They embrace, for example, improved vehicle/vessel
technology (including improvements to the gasoline engine, electric and hybrid low emission vehicles
and the development of alternative fuels), infrastructure quality, design and construction technology(including new techniques for building tunnels, bridges and earth embankment and cuttings) andinfrastructure management (including air traffic control systems, urban traffic demand management,
junction controls and intelligent transport systems).
The supply and management of transportation is too important to be left to the market,
especially given that transportation is a sector where the free market does not necessarily bring the
optimal social outcome. Transportation planning, therefore, deals with the ways in whichgovernments, at various levels, try to ensure that transportation effectively and efficiently moves
people and goods, shapes urban form, affects economic vitality and impacts quality of life to meetwider social objectives. It includes issues such as roadway congestion, transit services, and nonmotorized travel.
For all these reasons, European countries are mainly focusing on the integration of transportmodes, whose key factors lies in public transport quality, coordination and affordability and in thecollaboration among different institutional levels, as well as on a good presentation to the public (UKCommission for Integrated Transport, 2007). We will now illustrate these observations on the basisof an interesting case study in the Venice area, where integrated and intermodal options are a
prerequisite for accessibility and sustainability in the local transport system.

Modal re-balance and intermodal integration for sustainable transportation systems
The aim of the present paper is to present the results of a study carried out in the city of
Venice in which a modal re-balance and intermodal integration have been experimented to increase
the sustainability of the existing transportation system. As previously stated, if it is clear that thepathway to a more sustainable transportation system has to take into account a strong reduction of
the private cars’ circulation, it is not as clear how to make this feasible. A universal recipe still does
not exist, even though several policies have been variously tested in the world. In a recent study(Garling and Schuitema, 2007) the authors have analyzed the impact of several travel demand
management measures and have concluded that the only way to make such measures effective is tocombine together coercive and non-coercive ones, i.e. introducing obstacles to car usage butcontemporary increasing the attractiveness of the other transportation modes. In this light an
important role to achieve a sustainable mobility is played by a mix of policies of intermodal
integration and modal re-balance.
This idea of modal reconfiguration is also confirmed elsewhere. In particular in Potter andSkinner (2000), an interesting perspective is proposed in which transport planning should follow aholistic objective-led approach. The basic idea is that an effective planning has to take into account all
the dimensions of the travel choices: the choice of travelling, the choice of the destination, the2choice of the mode and finally the choice of the path. Only by regulating all these dimensions it ispossible to create a well organized system. Despite being very interesting this idea is not very easily
implementable, above all because the personal choices are very difficult to be identified andinfluenced. However, the idea of integrated planning is becoming fashionable and can be used on acase study by case study approach to be adapted in the best possible way.
Another interesting analysis carried out concerns the Greater Toronto Areas (Kennedy, 2002)
and calls for a new transportation system organization in which a mixture of modes have to be
managed at once. Also, in other studies (see e.g. Musso et al., 2008), the steps followed in the Italian
cities of Rome and Napoli to improve the cities’ environmental conditions and liveability and the role
played by the integration of all transportation modes of the city are described.
In conclusion, there is a common perspective to highlight: in order to obtain a transportation
system that at the same time is as efficient as possible and wastes as few human resources as
possible (in one word a sustainable transportation system), a high level planning approach isnecessary in which all relevant factors influencing the mobility in a certain area are considered andorganized together. In this light, this paper briefly presents an integrated approach that has been
adopted to design a feasible solution to the congestion problems of the city of Venice.
As will be detailed in the remainder, the proposal of the integrated policy intervention in
Venice is based on the construction of a sublagoon tube connection between Venice island and themainland. The analyses in our paper are focused on the impacts on the modal split of the new accessmode to the Venice island (i.e., the Historic City) and of the new inter-modal terminal on the only
mainland access point, where the terminal, connected to the airport station, will also integrate theRegional Metropolitan Rail System and the highway system. The study represents an illustrative caseof the chance of incisively impacting on the integrated land-use/transport system by means ofsustainable mobility measures, aimed at modal re-balance and inter-modal integration. Suchevidence has been magnified by the peculiarity of Venice, which represents a unique laboratory forexperimenting sustainable mobility policies, due to its morphological, urban, social and land use
characteristics.
Simulations carried out in the study allowed identifying the most suitable layout of the sublagoon tube and the best localisation of the metro stations. The main evaluation criteria used are (i)the reduction of the total “running” time, (ii) the increase of the revenues for the areas impacted by
the project and (iii) the reduction of pollution due to minor private car traffic flows. The outcomes
are then used to evaluate the integration of the sub-lagoon tube within the wider transportation
system of the area, first looking at quantitative indicators directly derived from the simulations of thetransportation system, and then performing a multicriteria analysis of the scenarios by means of theRegime method. The attractiveness of the new metro system has been the key factor in our analysis,
indeed leading to traffic reduction on the existing networks, and, subsequently, to a decreasing
negative impact on existing social and environmental issues.

3The island of Venice: setting the scene
The uniqueness of the city of Venice for experimenting sustainable mobility policies is highlighted bydifferent factors. First of all, the city of Venice is composed by 118 small islands connected by meansof 354 bridges and divided by 177 channels. For these unique geographic features the transport
supply of the city is, by nature, an intermodal supply. The access from mainland to the HistoricCentre (HC) is allowed by lagoon boat services, or alternatively by the only available land connection,
the “Ponte della Libertà” (Fredoom Bridge), which gathers a rail public service and the road transport,
both for private use and for transit lines. Once reached the HC, the transport alternatives reduce tocanal boat services and to pedestrian mobility. Hence, movements towards internal destinations of
the HC may be fulfilled only as trip chains involving at least two transport modes.
Secondly, the transportation demand pattern in the island is peculiar as well. Very few
inhabitants still live on the islands. Actually, the city is dominated by a lot of economic activities andtouristic attractions. For this reason there exist two main demand categories for trip purposes, workand tourism. They have roughly the same weight but, of course, are really different both for the dailyand seasonal trends and for the underlying behaviours in travel choices.
Moreover, the very high number of daily commuters who reach the island from VeneziaMestre (mainland) and the unique land connection to the HC lead to heavy congestion phenomenathat involve to large extent also the Mestre road network on the mainland. Even the pedestrian
network of the city centre is affected by non-negligible congestion problems.
Finally, the environmental constraints in the area strongly influence the possibility to suitably
manage and modify the transportation system. In particular, the hypothetical opportunity toencourage the navigation of the bay and of the various channels of the city cannot be fulfilled. Boatmovements, indeed, must be limited in order to preserve the delicate microcosm of the lagoon andto limit damages to the ancient buildings caused by the wave motion.
For all these reasons, to study the impact of an important infrastructural intervention, like theconstruction of a sub-lagoon metro line, a detailed and careful scenario analysis is necessary.
The methodology used in this study has followed the typical path of a transportation study. In
particular, after the analysis of the current transportation system and the definition of the scenariosof intervention, a simulation of the transportation system has been performed in the different
scenarios. The peculiarity of the used approach is related to the fact that variables like the best
localisation of the metro stations, that at this planning level are usually considered of minor
relevance, have been at the outset taken into account in order to identify the most suitable(sustainable) layout (if any) of the improved transportation system of the city of Venice.

The current transportation system
As anticipated above, the transportation system which connects Venice Island to the mainlandis composed by a road infrastructure as well as by a rail infrastructure: the “Ponte della Libertà”
bridge, a group of parking areas for cars and buses concentrated at the end of this bridge, and a setof docks for lagoon boats. Apart from the lagoon boat services, all the connections to the islands are4

focused towards the “Ponte della Libertà” bridge (Figure 1), with too much concentration ofvehicular and pedestrian traffic on the extreme points of the system (bridges, station, harbour);lagoon transportation services are rather slow (the maximum allowed speed in the lagoon is 6 knots),and not frequent; in particular, the system is influenced by the lack of a direct connection between
the island and the airport.

Figure 1 Current connections between Venice Island and the mainland
Moreover, the current configuration of the transportation system has led to an excessive
localisation of activities next to the bridge on the Island, while further zones, in particular the area ofArsenale, have been progressively abandoned, thus suffering nowadays of urban decay (Figure 1).
A lively debate about the urban recovery model of the Historic Centre of Venice has led to theformulation of the so-called P.r.u.s.t(Plan for the urban requalification and the sustainable

development of the land-use) for the lagoon area, which, among other things, claims the necessity of
the realisation of a new high frequency, not polluting, not too invasive transport connection,
between Tessera airport of Venice and the Arsenale area with a twofold aim: first, to reduce
congestion on the “Ponte della Libertà” bridge and the surrounding areas; secondly, to contribute to
the revitalization of the Arsenale area.
In order to evaluate the technical and financial feasibility of the initiative, the Municipality andthe Chamber of Commerce, Industry, Crafts and Agriculture (CCIAA) of Venice, have promoted a setof planning studies, of a technical, environmental, financial and economic nature; in particular, aspecific study (Torrieri et al., 2002) has been conducted on the system of the connections between
the Island and the mainland, in order to forecast traffic volumes on the new links, and to evaluate
the benefits useful for land-use, and the recoverable aliquot of the investment by means of the
management of the new transportation services.

5

The planned scenarios
Currently the connections of Venice Island (Figure 1) with the mainland (Mestre, and the coastof Cavallino) and with the other islands of the lagoon (Murano, Lido) are assured by the following
transportation services (Figure 2):—

National and regional rail services, based at the station of S. Lucia;—

Touristic bus services, based in Tronchetto, a small island connected to the “Pontedella Libertà” bridge;—

Public road transport services, based in Piazzale Roma;—

Private self-produced transport (cars and motorcycles) with parking areas localised
next to Piazzale Roma and the island of Tronchetto;—

Lagoon boat services, localised at the southern side of Mestre (Fusina); at thenorthern side of Mestre (Tessera); and at the eastern side of the lagoon (Punta
Sabbioni-Lido).

The planned intervention of the Sub-lagoon tube described above is included in a morecomprehensive strengthening program of the transportation system of the area, whose main
projects were:—

Implementation of the Regional Metropolitan System, in order to improve the public
rail transport services in the provincial area;—

Doubling of the highway link in Mestre, in order to reduce the congestion on the
peripheral road network of Mestre;—

Construction of an urban tram line in Mestre.

Figure 2 Location of the main transportation services

6

In this framework, the realization of the Sub-lagoon tube, with its new terminal point inTessera, aims at strengthening public transport in the Venice area, by offering an alternative to bothcurrent individual users of private transport, and to tourists who reach the Island by bus, thus
providing a real alternative to the terminal of Piazzale Roma.

Figure 3 Scheme of the designed lines of the Sub-lagoon projectIn particular, the project includes the construction of an underground metro line in the lagoon,
allowing the circulation of vehicles of average dimensions and capacity (150-200 seats), articulated in
the construction of three lines, as described in Figure 3:—

Line 1 (L1), with two stations on the mainland (Tessera Airport and Terminal Tessera),a stop on Murano island, three stops on Venice island (Cannaregio, Fondamenta
Nuove, Arsenale);—Line 2 (L2), continuing from Line 1 towards the Island of Lido with stops in Arsenale,
Giardini di S Elena, S.M. Elisabetta, and Aeroporto “Nicelli” (Lido);—

Line 3 (L3), adding the following stops to Line 2: S.Lucia, Dorsoduro, Fusina

It goes without saying that the plans for such an ambitious underground system call for asystematic assessment and evaluation. We will present here now the various choice possibilities in
the form of a policy scenario analysis. For what concerns the evaluation scenarios, the following
configurations have been considered:—scenario 0: the system in the current situation is simulated and integrated with theworks in progress on the existing transport infrastructures (Regional Metropolitan
Service, Highway link of Mestre, Tram line).

—

scenario 1 (L1): the designed system is simulated, with the insertion of line L1:
Tessera-Murano- Arsenale, and the parking facility of Tessera; the beginning year forthe running of this service is set at T1=6 years.

7—

scenario 2 (L1+L2): includes the addition of a new stretch (line L2): ArsenaleAeroporto “Nicelli” (Lido); beginning year of the service is set at T2=T1+4—

scenario 3 (L1+L2+L3): the construction of line L3: Arsenale-S.Lucia-Dorsoduro-Fusina
is modelled and planned; beginning year of the service at T3=T1+14.

It is worth noting that the scenarios analysed are to be considered integrative and sequential,
rather than real alternative ones. In the next section, we will concisely present the underlying
transportation system model for Venice.

The integrated transportation system model
The study area and its traffic zones
The study area includes the entire territory of the province of Venice. The activities aresupposed to be localised in 398 zones, whose subdivision is described by previous official studies,according to the scheme in Table 1.
Table 1 Zoning of the study area
Venice Historic Centre

41(zoning adopted by Venice municipality)

Other lagoon islands

8(zoning adopted by Venice municipality)
36(zoning adopted by Venice Province)
314(zoning adopted by Venice Province)

Venezia Municipality(excluding islands)
Venice Province

The supply model
The transportation network of the Province of Venice is clearly multimodal. Despite thedifficulty of modelling all transportation modes together, it was indispensible to achieve a realistic
estimation of the effects of the new transportation system. For this reason the supply model iscomposed of the following infrastructures and services:• The private (self-produced) transport network: road network, parking areas,• The transit road network (buses)• The transit rail network (trains)• The pedestrian network on Venice island• The lagoon boat services network.
Clearly, the current railway network has not been considered in the simulations, because thepart of the traffic demand that may be attracted from the new transportation system may beconsidered rather marginal. Indeed, the railway system is mainly used by passengers (commuters,
visitors) that reach the city of Venice directly from outer parts of the province or even from otherprovinces, without stopping in Mestre. On the other hand, the pedestrian network has been included,8

because the traffic in the future scenarios can be significantly influenced by the connections between
the sub-lagoon stations and the pedestrian roads on the island. In our future scenarios, the networkmodel is integrated with the Sub-lagoon tube services. All network models have been represented bymeans of a geo-referenced oriented graph. We will now briefly describe the various submodels.
The road network
The road network comprises the main road infrastructures of the Province of Venice. It
obviously does not include any road in the city centre of Venice, since there isn’t any. For each link,
the following characteristics have been considered:•

Length, width and number of lanes;•

Capacity for each direction, defined as the maximum number of vehicles that in a hourcan pass through the road link, excluding preferential lanes, and the lanes exclusively
dedicated to the residents in the historic centre;•

The average free flow speed;•

The travel time on the link. This obviously depends on the traffic flow that exists on
the link. For this reason, for each link two values of travel time have been considered,
one corresponding to the expected average flow during the peak period and the otherduring the off-peak period. Its value has been obtained using the standard BPR model(U.S. Bureau of Public Roads, 1964);•

The average delay at the signalized intersections and at the level crossings (queuinglinks), in both peak and off-peak hours.

The road transit network (buses)
A specific local transit network was not created. The demand estimated for the transit system
was considered to be allocated over the entire road network. For the Venice area, this hypothesis
was necessary, since it is not meaningful to evaluate a future scenario (that certainly will influence
the future transit lines’ layout) on the basis of the present lines which, for example, do not allow
passengers to reach new destinations foreseen in the new project plan. In this light, simulation
results are useful to design the transit lines’ layout most desired by the users (thus most attractive) in
the future.
The pedestrian network
The pedestrian network was only implemented for the city centre of Venice. Each link of thepedestrian network has been given a constant speed of 4 Km/h. Clearly, in common practicepedestrian networks are considered usually uncongested, but in this case this is not always realistic
due to the large number of people that daily walk on the narrow streets of the city. However, thissimplistic hypothesis has been maintained in the study (although by means of a sensitivity analysis
this could be further investigated).
The lagoon boat services network

9The lagoon boat services network has been implemented by means of an oriented georeferenced graph, whose nodes represent the docks and whose links represent the lagoon
connections. Each lagoon transport line is characterised by a specific commercial speed, that takes
into account the cumulative times (stop delays, part of journeys in accelerated, decelerated andregular motion) experienced along each path with the service frequencies. Speeds and frequencies
are deducted from the official time schedules of the agency (named ACTV) supplying thetransportation services.
As an example, in Figure 4 the pedestrian and lagoon boat services networks are schematicallyillustrated (in yellow and orange respectively).

Figure 4 Pedestrian and lagoon boat services networks of the island of Venice
The sub-lagoon tube network
The specification of the new transportation services offered by the tube system depends on
the particular technological choice. However, hypothesizing a system like a light rail transit, theperformance indicators considered for the vehicles have been the ones reported in Table 2, wherev m is the average speed on the link, and a m is the average acceleration.
Table 2 Performance indicators of the chosen vehicles
Normal speed links
vm
22
m/sec
am

1.3

m/sec2High speed linksvm
25 m/sec
am

1.3m/sec2The demand modelOn the basis of information from previous studies and surveys, the mobility demand among
lagoon islands and the mainland, as well its temporal, spatial and motivational characteristics are10

known. Also the modal split among the existing transportation services is known from previous
statistical information. In particular, the available data sources were the following:- Origin-Destination (O-D) matrix of light and heavy vehicles for the year 1998 (Province ofVenice);- Traffic counts on the road network of the Province of Venice for the year 2000 (ANAS, that is
the National Road Board);- Motivational survey for people entering the city centre in the year 1997 (Municipality/ACTV);- Lagoon boat passengers counts for the year 1997 (ACTV).
As a result of the availability and statistical analysis of this huge amount of data, it was possible
to obtain the complete O/D matrix for the Province of Venice, as well as to retrieve the temporal,
spatial and motivational characteristics of the traffic demand. In the following figures and tables, themain results of this experiment are summarized.
In Table 3, the matrix dimensions and the aggregated daily volumes are reported. These data
are here shown to give the reader an idea of entire traffic pattern within the region.
In Figure 5 the spatial characterisation of the traffic demand in the city centre is shown. In
particular, the traffic zones attracting the highest demand in the Historic Centre (HS) are S. Marco, S.
Croce, Dorsoduro, Castello and S. Paolo. Among these, S. Marco and Castello particularly suffer fromthe distance to the only access point of the city and these zones are supposed to be, together with S.
Paolo, the traffic zones that will benefit most from the introduction of the new transit system.
Table 3 Pedestrian and vehicular daily average volumes directed to the lagoon islands and passed
through the “Ponte della Libertà” bridge (2002)
Current daily demand volumes towards Historic Centre of Venice (HS)Access mode to the HS
O/D Matrix dimension
Daily volume
Private road transport
350 × 49
19 855 pax
Road transit
350 × 49
37 559 pax
Rail transit
1 × 41
23 681 pax
Tourist buses
4×2
12 443 pax
Lagoon navigation Lido-P.ta Sabbioni
1 × 41
12 728 pax
Lagoon navigation from Tessera
1 × 41600 pax
Total daily volume of pax entering HS
350 × 49
106 866 pax
Current daily demand volumes in the study area
Access mode to the HS
O/D Matrix dimension
Daily volume
Private road transport
350 × 350
980 657 light vehicles
106 581 heavy vehicles

Considering the variability of the seasonal cycle (Figure 6), we may argue that the traffic
volumes reported in Table 4, referred to an average annual day, can be considered valid for 310 dayson average, so that for these circumstances the annual volume can be obtained by multiplying thedaily volume with a factor of 310. To calculate the overall volumes two characteristic periods areincluded in Table 4:11—

The peak period lasting 6 hours, in which about 70% of the daily average traffic is
registered.

—

The off-peak period, lasting 8 hours, in which about 30% of the daily average traffic is
registered.

The remaining 11 hours, occurring during the night, are of course not considered in the analysis,
because they are not interesting for the purpose of the study.

Figure 5 Mobility distribution subdivided by destination in the lagoon

Average daily presences

60,00050,00040,00030,00020,00010,0000
Jan Feb Mar Apr May Jun

Jul

Aug Sep Oct Nov Dec

Month

Figure 6 Yearly mobility trend (Venezia – Historic Centre 2000-2001)
Table 4 Peak and off-peak period traffic volumes
Peak
hours
Off-peak
hours
Total

Average annual daily traffic (veh)Hourly traffic (veh)%11,272

1,879

11.61

4,909

614

3.79

16,181

2,493

12

The motivational characteristics regard almost completely the drivers of systematic trips andthe trips of tourists visiting the region. For both motivations the demand elasticity with respect to the
supplied performances can be assumed about null.

The integrated traffic forecasting model
Expected growth
On the basis of surveyed historical trends and existing previous studies about mobility patterns
in the study area, the trend curve has been estimated and presented in Figure 7 by means of alogistic model. It indicates that the growth in 20 years is equal to 15% of the registered volume of
2003.
140
120
100

People (x1000)

80
60
40

data
dati
estim.
stime

20
0
1980

1990

2000

2010

2020

Year

2030

Figure 7 Trend curve of mobility of travellers entering the Island of Venice

Simulation experiments
After the design of the supply model for the whole transportation system and after theestimation of the traffic demand, the different scenarios described above have been simulated bymeans of the (commercial) software TransCAD (Caliper Corporation, 2005). For each scenario, twosimulations have been performed, one for the peak period and the other one for the off-peak period.
Moreover, the traffic assignment to the network has been performed in two steps. First, a
Stochastic User Equilibrium assignment has been performed on the entire network (with thevehicular demand matrix whose dimensions were 350×350, because the city of Venice wasrepresented by only one point) to identify the equilibrium configuration of the flows on the road
network; then a stochastic network loading (with constant costs equal to the ones obtained as theoutput from the first assignment) has been performed on the multimodal network to identify thepath (and modes) chosen to reach the city centre (in this case the demand matrix was the complete
matrix of passengers directed to the city centre and therefore its dimensions were 350×49). In thisway it was possible to identify the vehicle and passenger flows on the whole network.
The traffic implications of the new transportation system were assessed comparing the resultsof the different scenarios. In the remainder, several interesting outcomes are reported. In Table 5 the13percentage of passengers detracted from the existing transport modes by the Sublagoon Tube inscenario 1 is highlighted.
Table 5 Percentage of passengers detracted from the existing transport modes by the Sublagoon Tubein L1 scenario
SUBLAGOON TUBE traffic volume

Scenario 1

From tourist buses
From cars and motorcycles
From transit system
From lagoon boat services from P.ta Sabbioni to Lido
From lagoon boat services Tessera
TOTAL SUB-LAGOON TUBE (L1)

4.68%
6.98%
4.66%
-0.61%
16.93%In Figure 8, the distribution of the traffic volume attracted for each traffic zone per different
access mode is reported. As expected, the higher the distance of the zone from the Ponte della
Libertà bridge, the higher is the percentage of passengers using the sub-lagoon tube connection.
Next, in Table 6 the estimated traffic volumes in all three future scenarios are reported for the
sub-lagoon line as well as for the other access modes to the historic centre. It is evident from theseresults to recognize that in Scenario 2 the Sub-Lagoon system is already the most used access modeto the city of Venice.
The estimated data offer also the possibility to design the supplied service capacity in the peakhour period, proportional to the maximum expected value in the 20-years projection (in particular,
the maximum estimated value is about 2326 pax/hour per flow direction). It is worth noting that thetraffic estimates on the L1 line after thirty years are more or less constant, regardless of the presenceof the lines L2 and L3; the same holds for line L2, in the presence of line L3. It is thus clear consideringthat the three evaluation scenarios are, as anticipated above, integrative alternatives.

Figure 8 Traffic volume by destination to the historic centre per access mode: L1

14

Figure 9 further clarifies what was already stated before: in scenario L3 the integration of alltransportation modes and the implementation of the three lines of the sub-lagoon transit systemallow the fulfilment of a balanced distribution of the traffic among the available transportation
modes. In particular, as it is clearly shown, only few people are forced to walk a long distance toreach their destination. Moreover, the zones of the islands closer to the Arsenale appear now to bevery close to the airport and this will surely influence their future development.
Table 6 Average daily traffic per access mode to the historic centre (passengers)
Ex-AnteT1
6

Ex-Post
T2
T3
10
20

-

7 885

8 371

Projection years for each scenario 00
Access mode to the historic centreLine

Line L1: n° of from cars and motorcycles
access points from tourist buses

9 852

-

5 284

5 499

6 074

at thefrom public extra-urban road transport

-

-

-

-

terminal of

from public urban road transport

-

5 267

5 757

6 428

TesseraFrom lagoon transport services P,ta Sabbioni - Lido--

From lagoon transport services Tessera
Total SUBLAGOON TUBE (terminal of Tessera)-

684
19 120711
20 338786
23 140

-

-

-

-

-

-

-

-

at the Lidofrom public extra-urban road transport

-

-

-

-

stop

from public urban road transport

-

-

-

-

From lagoon transport services P,ta Sabbioni - Lido--

13 75315 191

From lagoon transport services - Tessera

-

-

-

-

Total SUBLAGOON TUBE (stop of Lido)Line L2 n° of from cars and motorcycles
access points from tourist buses

-

-

-

13 75315 191

Line L3 n° of from cars and motorcycles

-

-

-

4 005

access points from tourist buses
from public extra-urban road transport
from the

-

-

-

9 103

-

-

-

-

-

-

-

3 902

Malcontenta From lagoon transport services P,ta Sabbioni - Lido
From lagoon transport services - Tessera

-

-

-

-

-

-

-

-

Total SUBLAGOON TUBE (stop of Malcontenta)

-

-

-

17 009terminal of

from public urban road transport

Total SUB-LAGOON TUBE
cars and motorcycles (P.le Roma and Tronchetto)
touristic buses (P.le Roma and Tronchetto)
extra-urban road transit (P.le Roma and Tronchetto)
urban road transit (P.le Roma and Tronchetto)
tram (P.le Roma and Tronchetto)lagoon transport services from P.ta Sabbioni to Lido
lagoon transport services - Tessera
rail transport-16.93% 29.00% 42.62%
18.63% 11.65% 11.51% 7.96%
11.69% 7.01% 7.01% 0.00%
20.98% 20.98% 20.98% 20.98%
13.88% 9.22% 8.98% 0.00%---5.92%
11.96% 11.96% 0.26% 0.26%
0.61% 0.00% 0.00% 0.00%
22.25% 22.25% 22.25% 22.25%

TOTAL

100% 100% 100% 100%

For what concerns the expected impacts of the project, Figure 10 shows how the travel time
distribution between the HS zones (by foot) changes, and this translates into significantly lower
values.

15

Figure 9 Traffic flows entering the historic centre of Venice with the Sub-lagoon line L1, L2 and L3.
14
12Frequency

10
8
6
4
2
0
0

5

10

15

30

45

60

> 60

Travel Time [min]Scenario
1
Pontedella Libertà+ Sublagunare

Pontedella 0LibertàScenario

Figure 10 Pedestrian travel time distribution within the city centre with and without the Sub-lagoon
line L1

Expected impacts of the projectIn this section, the expected impacts from the Venice project will be further investigated.
According to the general aims of the study, these impacts can be summarised as:•a reduction of the total running times in the connections with the Island of Venice;•a increase in income for the areas affected by the project;•a reduction in pollution due to lower private car traffic flows.

In Table 8 the reduction of the travel times is presented, for the two different demand
categories distinguished. Considering a value of time equal to 0,065 €/min (i.e. the value of around4€/h commonly used in transportation studies in which only one user’s category is considered), and16

assuming a zero economic value to the saved time by occasional users, then the economic value ofthe total time savings is at least equal to 10,2 million €.
Table 8 Average travel times saved for different demand categories in Scenario 3.
Saved travel times per
trip
(min)

Demand category
Systematic trips/ from cars
Systematic trips/ from transit
Non-systematic trips

Minutes
21,4
14,0
25,4

The environmental benefit is tied to the reduction of pollution, noise, accident rates, andgreenhouse gases. In a complementary study (see Torrieri et al., 2002) this was given an economic
value ranging between 50 and 100 millions €/year.
The increase in income is assessed in relation to the induced activities in the areas served by
the Sub-lagoon Tube. Assuming a start-up of about 100 new firms in the Historic Centre, and 30 new
firms in Murano, this leads to an added value of about 34,3 mllions € in 20 years.
The estimated net present value 3 of the benefits generated by the Sub-lagoon tube
intervention in 20 years, is reported in Table 9, for each category of benefit. Here, the revenues fromthe traffic system have been evaluated on the basis of the following assumptions on the fare system:•

Systematic users:

2 (€/trip)•

Occasional users

6 (€/trip)

Assuming a unitary net management cost equal to 3,3 €cent/(place km), the overall balance
sheet can be found in Table 10.
Table 9 Estimated net present value of the direct and indirect benefits generated by the Sub-lagoon
Tube in 20 years
Category

Actual benefits

%

Time

€ 138,422,661

20.67%

Income impacts€ 463,430,128

69.19%

Pollution reduction€ 67,951,632

10.14%

Total€ 669,804,421

100.00%

Table 10 Estimation of the balance sheet
Cash flows€/yearManagement costs

5,155,920

Revenues from traffic
Management profits

29,433,880
24,277,960

For what concerns the total cost of the investment, this has been estimated to be about 330
Millions €.

3

The rate of discount is assumed to be equal to 5% on a one year-basis.

17

Integrated multicriteria evaluation for the Venice sub-lagoon system
Introduction
Multicriteria analysis is an established decision support tool in decision and choice problems
that are characterized by (i) a set of distinct choice alternatives; (ii) a set of mutually incompatible(conflicting) decision criteria; (iii) the presence of different priorities (weights) attached to thevarious decision criteria; (iv) the need to identify ‘the best possible’ choice alternative. The
information necessary to perform a multicriteria analysis is normally included in a so-called effect(impact) matrix which contains the expected outcomes of each alternative to be considered for all
relevant choice criteria. In addition, it is necessary to have insight into the decision makers’
preferences for each of the decision criteria (see Munda, 2008).
The above presentation of a multicriteria analysis implies a systematic assessment of the
impact of the various alternatives. This impact assessment may include direct and indirect impacts,
short-term and long-term impacts as well as social or geographical distributions of such impacts. It
goes without saying that a solid impact assessment lies at the heart of any multicriteria analysis andcalls for a balanced operational methodology including sensitivity analysis and feedback
presentations of relevant stakeholders.
In addition, the estimation of a decision-maker’s preference structure (weights set) is a central
element in each multicriteria analysis. This can be based on stated preference techniques,posteriority analysis, simulation analysis etc. Especially in a multi-decision-maker context, theassessment of weights is not easy, reason why in practice often ‘fictitious’ weights are deployed inorder to analyze ‘what-if’ conditions.
Another critical element in multicriteris analysis is the level of measurement of both theimpact (effect) table and the weights set. The precision of measurement may range from cardinal toordinal information, from crisp to fuzzy information, and may also contain alpha numericalinformation. The level of measurement is essential for the type of methodology to be used in a
multicriteria analysis. In the past decades, dozens of multicriteria decision support tools have beendeveloped, each with commonalities but also differences regarding the treatment of the information(see for a review inter alia Munda, 2008 and Nijkamp et al., 1990). A wide variety of software
packages has in the meantime been developed to offer an operational decision support system toplanners and decision-makers.
Multicriteria analysis has over the past decades been applied tio a wide array of evaluation
problems, for example, in the field of environmental management, energy policy, industrial planning,land use planning, public facilities management and so forth. It has also found a wide application in
the field of transportation planning.
Transportation provides many illustrations of the applicability of multicriteria analysis incomplex decision-making. Transportation projects are usually discrete choice projects, which have avariety of relevant dimensions for balanced and multi-faceted decision-making, such as cost items,
security and safety aspects, land use dimensions, environmental factors, social (distributive)

18

elements, etc. In the literature on transportation planning many examples of the application ofmulticriteria analysis can be found. In the following section, the hierarchical Regime method(Hinloopen and Nijkamp, 1990) will be applied to evaluate the scenarios discussed so far.

Regime analysis
The hierarchical Regime analysis is able to deal with both qualitative and quantitative plan or
project effects. In our scenarios, the cost/benefit indicators are numerical in nature, but as there aresome missing data, we have preferred to transform such cardinal information into rank orderinformation, in order to consistently compare the outcomes. The total effect matrix related to our
project assessment model is presented in Table 11, where all entries have a positive meaning (i.e.,the higher, the better).
Table 11 Effect Table for Regime Analysis
Nr. Effects

Scenario
0

L1

L2

L3

1 Average network speed

1

3

3

4

2 Total kilometres made by cars directed towards HS
3 Total kilometres made by tourist buses directed towards HS
4 Total kilometres made by heavy vehicles directed towards HS

1
1
1

3
3
3

3
3
3

4
4
4

5
6
7
8

Total travel time – cars
Total travel time – tourist buses
Total travel time – lagoon boats Tessera
Total travel time – lagoon boats Lido

1
1
1
1

3
3
2
1

3
3
3
3

4
4
4
4

9 Average value of congestion (VOC) (peak hour)
10 Percentage of saturated links
11 Total Vehicles km (VKT) – peak hour

1
1
1

1
3
3

1
3
3

1
4
4

12 Percentage of passengers reaching HC with the Sub-lagoon
Tube
13 Percentage of traffic volume using Sub-lagoon Tube

1

2

3

4

1

2

3

4

14 Investment cost

4

3

2

1

15 Time savings

1

3

3

4

16 Income impacts

1

2

3

4

17 Pollution reduction

1

3

3

4

Our hierarchical multicriteria analysis using the Regime method was implemented in a
stepwise (hierarchical) way by grouping together first the effects regarding total kilometers (2-3-4);
then, the effects regarding the total travel time (5-6-7-8), the effects related to congestion (9-10-11),
and the effects regarding traffic volume (12-13). Thus, a Regime analysis was applied to each of these
subsets. The analysis was carried out without assigning weights to the effects. Next, the overall
Regime method was applied to the remaining aggregate effect matrix.

19

The outcomes, illustrated in Figure 11, show that the most preferable scenario is L3. These
results confirm the plausibility of the cost-benefit analysis, using as indicators the Net Present Value(NPV) and the Internal Rate of Return (IRR). From a financial perspective, the NPV is negative without
any public investment. With a public financing of about 30%, the NPV becomes positive and the IRR
assumes a value of about 7%. From an economic perspective, the NPV is positive and the IRR isestimated around 14%.
These results support obviously the Public Authority decision of considering the public utility ofthe project concerned and to promote its realization on the basis of project financing supported witha 30% public investment involvement.

1
1
0.9
0.8

0.667

0.7
0.6
0.5

0.333

0.4
0.3
0.2
0.1

0

0
Scenario 0

L1

L2

L3

Figure 11 Predicted performance index for each scenario by means of Regime analysis.

Conclusions
In this paper, the main outcomes of a feasibility study regarding an integrated newtransportation infrastructure for the city of Venice have been presented, with particular attention forthe part of the study related to the current and future organization of the intermodal transportation
system of the area. After a brief overview in which the integration of different transport modes has
been considered as a possible significant contribution to the challenge of sustainability, the case of
Venice has been presented as an illustrative case, even though it is full of peculiarities due to thephysical morphology, the demand pattern and the multimodal structure of the study area.
The case study presented here, although still lacking a comprehensive methodology for the
impact evaluation, is interesting for different reasons. First, it has brought to light some of the usual
contradictions in the decision-making process: supported by earlier decisions stated in official urban

20

plans, the project has been the object of a complex and broad feasibility study, requiring research
efforts from several panels of experts in the field of transportation and economic evaluation, as wellas the use of time and financial resources. Such studies, as explained in our study, have predicted thesuccess of the application of a multimodal approach from different points of view. Nevertheless,since 2002 the project is still not ready for implementation, due to the difficulties encountered in the
public debate with several private and public stakeholders involved, as well as due to lack of bothprivate and public funds.
Secondly, the above mentioned general urban plan, promoting multimodal and integrated
approaches to the transportation system management, has allowed and encouraged the fulfillmentof an in-depth analysis whose main outcomes, presented in this paper, have highlighted thenecessity of the planned approach in order to solve effectively the problems of congestion, pollution
and progressive urban decay of some areas of the city of Venice.
Thirdly, the study confirms the need for a clear future perspective for the area concerned, inorder to assess the feasibility as well as the sustainability of the foreseen investments. Indeed,looking only at the financial indicators, there is no evidence of significant and sufficient financial
benefits: the project is worth realizing only if we consider the economic translation of social andenvironmental benefits. This emphasizes moreover the importance, already stated by several studies(see for example Brons, 2006), of developing more reliable and precise methods for the evaluation
for the economic impact of new transportation infrastructures.
It is evident that further steps are still needed to complete the study, including the use of finetuned indicators to perform a solid and comparative methodology for the evaluation of the impactsof the new public transport investment plan.
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