Resilience Assessment of a Twin-Tube Motorway Tunnel in the Event of a Traffic Accident or Fire in a Tube

Abstract

We have developed a traffic simulation model to quantitatively assess the resilience of a twin-tube motorway tunnel in the event of traffic accident or fire occurring within a tube. The motorway section containing the tunnel was investigated for different possible scenarios including its partial or complete closure. The functionality of the road infrastructure, in the case of an accident in one of the two tubes (each tube presents two lanes with unidirectional traffic under ordinary conditions), was assumed to be recovered both by using the remaining undisrupted lane of the tube interested by the disruptive event (only one lane is closed) and reorganizing the traffic flow by utilizing the adjacent tube for bi-directional traffic (both lanes are closed). The effects of an alternative itinerary individualized in the corresponding open road network were also examined. The level of functionality of the system during the period in which the tube is partially or completely closed was computed as the ratio between the average travel time required to reach a given destination from a specific origin before and after the occurrence of the disruptive event. The resilience metrics were assumed to be resilience loss, recovery speed, and resilience index. The best scenario was found to be the partial closure of the tube in contrast to the complete one. However, in order to contain the negative effects on the functionality of the motorway section due to the complete closure of the tube, it is worth highlighting how the traffic by-pass before the entrance portal of the closed tube should be open in a very short time by the tunnel management team to allow for the quick use of the adjacent tube for bi-directional traffic. An additional improvement, with reference exclusively to passenger cars traveling through the adjacent unblocked tube, might be obtained by activating the variable message signs, located at a sufficient distance from the motorway junction before the entrance portal of the closed tube, in order to suggest an alternative route to heavy good vehicles (HGVs) only. Whereas, when the alternative itinerary is used by all vehicles traveling towards the blocked tube (i.e., both passenger cars and HGVs), this redirectioning of the motorway traffic flow was found to be characterized by an excessive travel time, with it therefore not being advisable. The results obtained might be useful as a decision-making support tool aimed at improving the resilience of twin-tube tunnels.

A Simultaneous Analysis of the User Safety and Resilience of a Twin-Tube Road Tunnel

“…In our previous study [25], we assumed that the occurrence of a traffic accident in the north tube would lead to different potential scenarios involving its partial or complete closure for 1 h, 2 h, or 3 h (however, in this investigation, we considered the worst-case scenario, which was a closure of 3 h). Specifically, the functionality of the investigated twin-tube motorway tunnel, after the occurrence of a traffic accident in the north tube, was assumed to be restored by utilizing the remaining available lane of the north tube (i.e., only one lane is closed) or rearranging the traffic flow using the south tube for two-way traffic (i.e., both lanes of the north tube are closed).…”

“…PIARC [23] presented the current state of knowledge of road tunnel resilience, whereas Borghetti et al [24] investigated the resilience and emergency management of road tunnels. Finally, Caliendo et al [25] set up a traffic simulation model for evaluating the resilience of a twin-tube motorway tunnel in the case of a traffic accident in a tube.…”

“…However, it is worth highlighting that, among the studies referred to, only a few have focused specifically on the resilience of road tunnels, such as Liao et al [12], Khetwal et al [21], PIARC [23], Borghetti et al [24], and Caliendo et al [25].…”

“…With reference to our previous studies, it is also worth highlighting that we did not investigate user safety in the earlier paper [25], while in other studies, we evaluated only the safety level of tunnel users in the event of a fire (e.g., Caliendo et al [26][27][28][29][30][31][32], Caliendo and De Guglielmo [33][34][35][36], and Caliendo and Genovese [37]), but not resilience. In other words, tunnel resilience and user safety were not coupled to each other; consequently, the effects of a strategy to recover the functionality of a tunnel that might influence user safety or vice versa were not considered.…”

Use of Universal Simulation Software Tools for Optimization of Signal Plans at Urban Intersections

“…At present, the most common approach to solving tasks in various areas, not only in transport, is a computer simulation [17]. The simulation approach to setting up traffic lights is advantageously used mainly in cases where we need to optimize traffic lights without large investments in infrastructure.…”