With the aim of investigating under which demand levels and daily distribution, the impact of interpersonal distancing could lead to the over-saturation of Public Transportation systems either on-board vehicles or at the stations, the simulation-based procedure shown in Figure 3 was proposed.
Two case studies with a different seat reservation system have been considered: a suburban railway line where no seat reservation is required, and a High-speed Rail (HSR) line for which seat reservation is mandatory. Different criticalities might be arising in the two cases: in the former (suburban line case) train could get overcrowded and therefore not compliant with the interpersonal distancing provisions; in the second case (HSR line) part of the potential demand might be unsatisfied due to seats unavailability, and, in turn, be shifted to others modes with consequent loss of revenue for the operators.
From the demand side, the PRE-COVID scenario with passenger flows level equal to those prior to the lockdown was taken as the upper bound, while the PHASE 1 scenario was taken as the lower bound with only essential activities re-opened and assuming very low demand level (i.e. those observed in the first days after the lockdown). The intermediate demand scenarios have been built up by considering a gradual relaxation of the restrictions on activities and trips.
3.1 The case of the sub-urban railway line S13
The S13 suburban railway line connects Bovisa (Milan) with Pavia passing through the city center of Milan. Figure 4 shows in detail the path of the line, including stops and interconnections with other public transportation services.
The reconstruction of the PRE-COVID and PHASE 1 scenarios was based on historical data relating to boarded and alighted passengers at each station and for each train. Data analyzed for the PRE-COVID scenario were related to November 2019, while data for the PHASE-1 scenario refer to March 2020. A reduction of the maximum number of on-board passengers in a working day of about 79% is observed from the PRE-COVID scenario to the PHASE-1 scenario, for both directions Pavia-Mi Bovisa and Mi Bovisa – Pavia (Figure 5). However, the structure of the demand did still present the same two peaks periods: a morning peak (from 6:30 to 9:00 am, on the Pavia – Mi Bovisa direction) and an evening peak (from 17:00 to 19:00 on the Mi Bovisa-Pavia direction).
In the simulated scenarios, in addition to the PRE-COVID and PHASE 1 scenarios, the following scenarios have been simulated:
- PARTIAL RE-OPENING, in which it is assumed a partial reopening of university and schools, i.e. half of the students attending in presence and half in distance mode, resulting in a demand level for study purpose of 50% less than that assumed in the PRE-COVID scenario;
- NO-STUDENTS, in which it is assumed that schools and university would be kept closed and teaching activities go entirely in distance mode, thus resulting in a null demand for study purpose in order to reduce trains loads in particular during the peak periods.
The estimated station-to-station OD matrices in the peak periods have been assigned to the trains using a schedule-based assignment model (Cascetta and Coppola, 2012) in order to estimate the flow on the trains operating in the morning (6:30-9:00) and evening (17:00-19:00) peak periods considered (Figure 6).
Service frequency and rolling stock ( i.e. “Treno Servizio Regionale”) TSR composed by five coaches 2 with a cab and a wheelchair bay for disable people (MCH) and the others without (M), are considered as invariant. A full train capacity, including all available seats and considering an occupancy rate of 4 passengers per square meter for the standing places, results in 960 passengers/train. The introduction of interpersonal distancing measures yields a train capacity of 270 passengers, assuming half of the seats available plus an aliquot of standees equal to the 10% of the seats available in normal conditions. Under these restrictions it can be observed a severe overload of the train in almost all the stations and for almost all the trains running in the peak periods.
Table 2 reports the aggregate results for the simulated scenarios, in terms of number of stations with departing trains in overcrowded conditions and of average number of passengers exceeding train capacity: even assuming zero trips for study purposes, there would be a number of stations (6 and 5 out of 13, respectively on the Pavia – Mi Bovisa and Mi Bovisa - Pavia direction) with departing trains exceeding the allowed capacity of 270 passengers, with an average number of overcrowding ranging between 12 and 47 passengers/train. These prove that the adoption of the interpersonal distancing is not sustainable even considering a complete limitation of students’ mobility.
Table 2 – Outputs of the scenario simulations with capacity restrictions (i.e. 270 passenger/train) under different assumption of demand levels.
Pavia – Bovisa (6:30-9:00)
|
|
Demand level
|
|
PRE-COVID
|
PARTIAL RE-OPENING
|
NO-STUDENTS
|
PHASE 1
|
Number of stations with oversaturated train (# stations)
|
11
|
9
|
6
|
0
|
Average number of passengers over train capacity (pax/train)
|
157
|
116
|
47
|
0
|
|
|
|
|
|
Bovisa – Pavia (17:00-19:00)
|
|
Demand level
|
|
PRE-COVID
|
PARTIAL RE-OPENING
|
NO-STUDENTS
|
PHASE 1
|
Number of stations with oversaturated train (# stations)
|
9
|
7
|
5
|
0
|
Average number of passengers over train capacity (pax/train)
|
102
|
48
|
12
|
0
|
3.2 The case of the HSR Lines: Milan-Rome-Naples
The Milan-Naples high-speed Rail (HSR) line connects some of the most attractive Italian cities, such as Bologna, Florence and Rome (Cascetta et al., 2013). In this study the direct services between Rome-Milan and Rome-Naples have been considered.
The invariant scenarios have been identified and assessed based on the timetable of HSR services offered by the two HSR undertakings, i.e. the incumbent Trenitalia and NTV (Nuovo Trasporto Viaggiatori): a decrease of about 90% of services per day was observed from the PRE-COVID to the PHASE 1 scenario (Figure 7).
With reference to the rolling stock, the two undertakings operate the service with different rolling stock: ETR500 and ETR1000 trains for Trenitalia, with a capacity of 597 and 467 seats, respectively; AGV575 and ETR675 trains for NTV, with capacities of 462 and 472 seats, respectively.
In the simulated scenarios, a capacity reduction of 50% of the seats available was considered due to the introduction of interpersonal distancing measures. Moreover, HSR service frequency has been assumed equal to 24 trains/day on the Milan-Rome line, and equal to 29 trains/day on the Rome-Naples one.
On the demand side, in addition to the PRE-COVID scenario, two scenarios have been simulated which respectively consider the 50% and 40% of the PRE-COVID demand level.
The supply-demand interaction has been simulated by means of a schedule-based run choice model (Cascetta & Coppola, 2012), allowing to estimating the on-board passengers for each train during the day. Figure 8 shows, for instance, the estimated demand flows in the Scenario 40%, disaggregated by hour-of-day, including those users that could not travel on HSR due to unavailability of seats (i.e. unsatisfied demand).
It can be observed that on the Rome-Milan and Milan-Rome directions there is quite a significative loss of passengers respectively 24% and 20% (i.e. unsatisfied demand), whereas on the Rome-Naples line this is limited only to the Naples to Rome direction, with a loss of 17%.
Table 3 shows the unsatisfied demand by section and direction in the simulated scenarios. It can be observed that:
- in all the simulated scenarios, the most affected sections are those connecting Rome and Milan;
- the unsatisfied demand is very significant when the volumes are assumed equal to those prior to the pandemic (PRE-COVID), with a peak of 62% on the Rome-Milan direction;
- in the reduced demand scenarios, the unsatisfied demand is between 20% and 30% on the Rome-Milan-Rome line and between 0% and 20% on the Rome-Naples-Rome line.
Table 3 – Percentages of passengers lost by HSR undertakings, in the simulated scenarios, for each direction.
Demand levels
|
Rome - Milan
|
Milan - Rome
|
|
Rome - Naples
|
Naples – Rome
|
PRE-COVID SCENARIO (100%)
|
62%
|
49%
|
|
38%
|
16%
|
SCENARIO 50%
|
30%
|
25%
|
|
19%
|
0%
|
SCENARIO 40%
|
24%
|
20%
|
|
17%
|
0%
|