Air curtain systems have been proposed as a supplementary smoke control strategy for vehicle tunnels, particularly where structural constraints limit the installation or upgrading of conventional ventilation systems. However, most previous studies rely on numerical simulations or fixed experimental facilities, while flexible experimental platforms and the influence of vehicle obstruction on smoke behavior remain less explored. This study experimentally investigates the smoke confinement performance of an air curtain using a 1:18 modular detachable scaled vehicle tunnel model. The modular configuration enables flexible assembly and adjustment of the experimental setup for different test conditions. A series of laboratory experiments was conducted using a liquefied petroleum gas (LPG) burner to simulate a vehicle fire. Temperature measurements and smoke visualization were performed under different air curtain jet velocities and vehicle obstruction conditions to analyze the interaction between the air curtain jet and buoyancy-driven smoke flow. The results show that the air curtain significantly restricts the upstream propagation of hot smoke and modifies the thermal field inside the tunnel. When the jet velocity reached approximately 5 m/s, the temperature in the protected region decreased by about 25–35% compared with the case without an air curtain. In addition, the presence of vehicle models altered the airflow structure and increased heat accumulation in the middle region of the tunnel cross-section. These results demonstrate that the proposed modular tunnel model provides a reliable experimental platform for tunnel fire research and highlights the importance of considering vehicle obstruction effects in tunnel smoke control studies.

Statistical Analysis of Vehicle Tunnel Fire Incidents in Zhejiang Province, China, from 2020 to 2024

The article examines the typology of underground transport structures, including pedestrian tunnels and crossings, motor vehicle tunnels, rail transport structures, and underground car parks and garages. It identifies the main trends in their formation. The analysis focuses on urban planning characteristics and architectural solutions, as well as identifying problems in the organisation of underground spaces in Lviv's pedestrian crossings. Based on the research, the paper reveals approaches to planning and modernising underground spaces in transport structures, focusing on sustainability, inclusiveness, functionality, comfort, safety and aesthetics. The results can inform urban and architectural planning approaches for the renovation of pedestrian underground crossings.

This paper presents a review of explosion mitigation techniques for road tunnels, with a focus on scenarios involving high-pressure hydrogen tank rupture under fire conditions. Both passive and active strategies are considered—including structural configurations (e.g., tunnel branching, vent openings, right-angle bends) and protective systems (e.g., drop-down perforated plates, high-performance fibre-reinforced cementitious composite (HPFRCC) panels)—to reduce blast impact on tunnel occupants and structures. The review highlights that while measures such as blast walls or energy-absorbing barriers can significantly attenuate blast pressures, an integrated approach addressing both blast load reduction and structural resilience is essential. This paper outlines how coupled computational fluid dynamics–finite element method (CFD–FEM) simulations can evaluate these mitigation methods, and we discuss design considerations (e.g., optimising barrier placement and tunnel geometry) for enhanced safety. The findings provide guidance for designing safer hydrogen vehicle tunnels, and they identify gaps for future research, including the need for experimental validation of combined CFD–FEM models in hydrogen fire–explosion scenarios.

Statistical Analysis of Vehicle Tunnel Fire Incidents in Zhejiang Province from 2020 to 2024

With the growing prevalence of lithium battery electric vehicles, the incidence of fires resulting from thermal runaway in lithium batteries is also on the rise. In contrast to conventional fuel vehicle fires, fires involving lithium battery electric vehicles exhibit distinct differences in fire dynamics, fire loads, and smoke characteristics. These variations impose more stringent requirements on the design of passive fire protection systems within tunnels. To evaluate the fire resistance performance of existing passive fire protection systems under electric vehicle fire conditions, this study first used PyroSim software 2022 (integrating FDS 6.7.9) to establish fire models for combustion engine trucks and electric trucks, comparing the combustion characteristics of both types of fires without insulation lining materials. Based on the electric truck fire model, different insulation lining materials were added. The analysis of the simulation results focused on the impact of the thermal conductivity and emissivity of each lining material on peak tunnel temperatures, aiming to identify the insulation lining material with the best fire resistance performance. The results indicate that the heat release rate, temperature distribution, toxic gas concentration, and smoke propagation of lithium battery combustion engine truck fires are all higher than those of combustion engine truck fires. Among the five insulation lining materials studied, SiO2 gel material demonstrated superior fire resistance compared to the others. This research provides a scientific and rational basis for tunnel fire protection design and fire response strategies, aiming to mitigate the damage caused by lithium battery electric vehicle fires to tunnel lining structures.

In megacities, road traffic is a major source of particulate matter (PM), requiring a critical understanding of effective air pollution control. Despite existing methods to determine PM emission factors (EFs) of vehicles, accurate estimation of PM emissions under real driving conditions remains challenging. We aimed to assess the EFs of organic aerosol (OA) and equivalent black carbon (eBC) from vehicles through on-road measurements in Seoul, Korea, to understand real-world PM emissions. We used a mobile laboratory equipped with an aerosol mass spectrometer and an aethalometer to measure the composition of PM. On-road measurements were conducted in vehicle tunnels, urban roadways, and residential areas, and the characteristics of measurement points were compared and analyzed. Our results showed that concentrations of OA increased proportionally with the influence of vehicle exhaust, while oxidation states of the OA decreased. Mobile measurements revealed spatial heterogeneities in aerosols, highlighting distinct characteristics of fresh OA on vehicle roads and elevated oxidation state values in residential areas. Active nitrate formation near vehicles led to elevated NO3 concentrations on roads compared to residential areas. Our study shows that mobile PM measurements, including OA and eBC, are valuable for the direct evaluation of emission inventories. However, given that the calculated EFs may not be applicable to other cities due to differences in vehicle composition and traffic conditions, the development of city-specific EFs will be necessary in the future. Furthermore, it is recommended to integrate this methodology with conventional emission inventories to identify vehicle-type-specific emissions.Graphical

The pipe jacking method is widely used in water supply and drainage, power tunnels, vehicle tunnel construction, and other fields. The main challenges include friction resistance, axis deviation, and environmental disturbance, especially when large-diameter pipes are jacked along the curve underwater. Based on a large-diameter pipe jacking project under Jinshan Lake, this paper records the settlement of surrounding structures, the jacking force, and the deviation in the axis and elevation during the jacking process. Furthermore, the factors affecting the monitoring data under different working conditions are studied, and the key points are concluded. The outcomes of the study will provide a reference and serve as a guidance for future related projects.

Abstract The submerged floating tunnel (SFT) is a newly developed traffic structure for crossing the long waterway. On the basis of the vehicle–tunnel coupled vibration, the vortex-induced effect o...

As an important part of urban rail transit, subway tunnels play an important role in alleviating traffic pressure in mega-cities. Identifying and locating damage to the tunnel structure as early as possible has important practical significance for maintaining the long-term safe operation of subway tunnels. Summarizing the current status and shortcomings of the structural health monitoring of subway tunnels, a very economical and effective monitoring program is proposed, which is to use the train vibration response to identify and locate the damage of the tunnel structure. Firstly, the control equation of vehicle–tunnel coupling vibration is established and its analytical solution is given as the theoretical basis of this paper. Then, a damage index based on the cumulative sum of wavelet packet energy change rate (TDISC) is proposed, and its process algorithm is given. Through the joint simulation of VI-Rail and ANSYS, a refined 3D train-tunnel coupled vibration model is established. In this model, different combined conditions of single damage and double damage verify the validity of the damage index. The effectiveness of this damage index was further verified through model tests, and the influence of vehicle speed and load on the algorithm was discussed. Numerical simulation and experimental results show that the TDISC can effectively locate the damage of the tunnel structure and has good robustness.

Motor Vehicle tunnels capture both direct emission and re-mobilized particles as well as gasses. These captured particles and gasses must be responsibly managed to ensure risks to human health are mitigated. Active air cleaning technologies which can remove particles and gasses are sometimes used in road tunnels. Passive air dispersal techniques are commonly used. In some rare instances Passive and Active systems are used together. Unfortunately, active air cleaning technologies are often NOT used once a project is approved and operating. In the absence of a passive ventilation strategy – not using the active ventilation system may result in a greater risk of harm to people than if no active air cleaning system was used at all. The best policy for managing the risks to human health from vehicle emissions is to ensure exposure is managed – by whatever method is best in the unique circumstances of each tunnel.

Assessing the Tenability Conditions for a Heavy Goods Vehicle Tunnel Fire under the Effects of Vehicular Blockage and Point Extraction Ventilation System

SummaryUnderstanding smoke temperature distributions and transport characteristics is of great importance to control and exhaust thermal‐driven smoke. However, previous studies have focused on this problem in plain areas, whereas ambient pressure decreases as elevation increases. This study investigates the influence of ambient pressure on the hot gas temperature distribution and movement characteristics in a tunnel fire. A series of numerical simulations are carried out in a vehicle tunnel with various heat release rates (HRRs) and ambient pressures. The results show that the maximum temperature and longitudinal temperature distribution under the tunnel ceiling increase with decreasing ambient pressure due to less heat loss caused by lower air density. In addition, the vertical temperatures of the smoke are slightly higher under lower ambient pressure, and this phenomenon makes the smoke spread slightly faster while the smoke layer thickness remains nearly the same under different ambient pressures. The results can provide a reference for tunnel lining design and ventilation arrangements in high‐altitude areas.

The objective of this study is to propose a new method to evaluate the performance of different evacuation modes, and to find a rational evacuation mode for long underwater vehicle tunnels. In this study, a combined evacuation model (TPES) incorporating both a traffic flow module and a crowd evacuation module is proposed to simulate the integrated crowd evacuation with the effects of traffic flow, and the model is partially validated by a field evacuation test and a verified model Simulex. A vehicle tunnel was modeled to simulate fire-related traffic congestion and passenger evacuation, and then the evacuation performance index Im of three evacuation modes in different fire situations were calculated. The results revealed that the hybrid evacuation mode performs best among the three modes, with Im superior to other two modes by up to 26%. The transversal evacuation passage mode performs better than the longitudinal mode under the same conditions. However, the transversal and longitudinal modes can be equivalent when the passage spacing difference is within a range of 150–200 m. The critical spacing of the evacuation passage in a simple evacuation process lies in between 100 m and 350 m at confidence level of 90% for the transversal evacuation mode.

터널환기 계획시 소요환기량은 환기시설 용량을 결정하기 위한 중요한 인자이며, 소요환기량 산정을 위한 차종별 오염 물질 배출량(환기설계를 위한 기준배출량)은 현재 환경부에서 제시하는 '제작차 허용배출 기준'을 근거하여 산정하고 있다. 그러나, 2013년부터 환경부에서는 자동차에서 배출되는 오염물질을 산정하기 위한 규정으로 '자동차 총 오염물질 배출량 산정방법에 관한 규정'을 고시하고 이 규정에 '자동차 차종별 배출계수'를 제시하고 있다. 따라서 도로터널의 소요환기량 산정시 이를 적용하는 것에 대한 검토가 필요한 실정이다. 본 연구에서는 2015년 경유차량의 배출가스 조작사건 이후 자동차 배출가스 규제강화에 따라 터널의 소요환기량 산정에 미치는 영향을 검토하였으며, 최근 환경부에서 개정한 '제작차 허용배출량 기준'과 '자동차 차종별 배출계수'에 의한 소요환기량과 EURO 배출기준을 적용한 소요환기량을 비교 분석하였다. 또한 소요환기량 산정 근거에 따른 합리적인 환기시스템 용량결정을 위한 기초 설계자료를 제공하는 것을 목적으로 한다. The amount of ventilation required in making the tunnel ventilation plan is an important factor for determining the capacity of the ventilation system. The amount of pollutant emission for each type of vehicle (basic emission amount for the design of ventilation volume) for estimating the required ventilation amount is based on the 'Standard for Allowing the Emission for the car manufacturing', proposed by Ministry of Environment. However, in 2013, the Ministry of Environment announced the 'Regulations on the calculation method of total emissions from vehicles' as a regulation for calculating the pollutants emitted from vehicles. In this regulation, there are the 'Emission factors for each type of vehicle'. Therefore, it is necessary to review the application of the Regulation to the estimation of the required ventilation volume for the road tunnel. In this study, the influence of the strengthened emission regulation in 2015 caused by the case of manipulation of emission volume for the diesel vehicle on the calculation of the required ventilation volume in the road tunnel has been checked. In addition, in this study, the required ventilation volume calculated according to the Standard for Allowing the Emission for the car manufacturing revised by Ministry of Environment and "Emission factors for each type of vehicle" and that calculated according to the EURO emission standard were compared for analysis. This study has implications that it provides the basic design data for calculating the reasonable ventilation capacity of the ventilation system based on the ground for calculating the required ventilation volume.

The health risks presented by noxious vehicle emissions inside tunnels has been amplified due to the increasing use of roadway tunnels. Particularly, for adjacent roadway tunnels, vehicular emissions from the upstream tunnel can further deteriorate the air quality within the following tunnels. A scale vehicle tunnel model was designed to experimentally modelled the airflow and pollutants dispersion in contiguous roadway tunnels. The channelling effect on pollutants dispersion between adjacent roadway tunnels was studied, and factors such as ventilation speed, open road section length, traffic condition (e.g. car free, car running and traffic congestion) were considered. Pollutants mass flow rate ratio between downstream and upstream tunnels was calculated to evaluate the variation of the entrained pollutants amount. For the car free condition, pollutant can be easily entrained into the downwind tunnel when the gap distance between roadway tunnels decreased. For the car running condition with fixed tunnel gap distance, the traffic speed variation barely changed the pollutants mass flow rate ratio. Furthermore, evident influences on pollutants concentration were observed from continuous congestion and partial congestion. Lastly, numerical simulation using computational fluid dynamics approach was conducted for the car free scenario, and reasonably good agreements were found for pollutants concentration ratio compared with the experimental data. The results yielded from this study further quantified the relationships among different influential factors on the pollutants dispersion between roadway tunnels, and can contribute to an improved tunnel ventilation system design, especially for the downstream tunnel.

The neutral erosion of lining concrete in vehicle tunnel under the condition of load and composite acid gases is noticeable. The anti-neutral analysis and prediction of an under-river tunnel lining concrete were discussed, and the neutral level was analyzed by a numerical way based on the effect of load level and composite acid gases. It was proposed that the anti-neutral level affected by moisture content exists a high and low range and the neutral depth increase with the increase of capillary porosity. Then the design method for highly anti-neutral lining concrete of vehicle tunnel was put forward based on the corrected carbonation depth. Finally the micro-structural parameters of highly anti-neutral lining concrete, such as moisture content, content of Ca(OH)2 and capillary porosity in concrete, were analyzed. The content of Ca(OH)2 was determined to be greater than or equal to the solubility of Ca(OH)2 under the condition of environmental temperature. The critical maximum connected capillary porosity was 9.15%. The research provides basis for the design and preparation of anti-neutral lining concrete of vehicle tunnel.

A study of wind effects on smoke extraction strategies in vehicle tunnels

This paper uses four different simple geometrical shapes to simulate a large-scale heavy goods vehicle (HGV) tunnel fire experiment using Fire Dynamics Simulator, version 6 (FDS6) in order to investigate the influence of using different fuel package shapes. Simulations also investigate the influence on temperature profiles when a large target is placed downstream of the fuel package. Predictions of flame extension, temperature profiles and gas species concentrations are compared with the experimental data. The use of the geometrical shapes causes significant differences in flame extension lengths during the fully developed fire phase. The variation in temperature predictions caused by using the different fuel shapes are insignificant when a large target is present behind the fire, however this is not the case if the target is omitted especially during the fully developed phase.

Computational fluid dynamics (CFD) simulations in 3D are performed to analyse the aerodynamic drag performance of a truck for two different on-highway road tunnel dimensions. The objective of this work is to investigate the aerodynamic drag performance of single- and multiple vehicle platooning configurations in single- and multi-lane one-way road traffic condition. Significant aerodynamic drag benefit is observed in no-traffic vehicle with an increase in gap between vehicle and road tunnel. In the vehicle platooning, the predicted aerodynamic drag benefit is up to 23% at lower vehicle separation. The aerodynamic drag benefit gradually drops in one-lane traffic and negative performance is observed from 60ft separation distance onwards. In two-lane traffic, where one vehicle is behind the other without a lateral separation, the predicted aerodynamic drag benefit is up to 60 and 44% at vehicle separation distance of 30 and 150ft, respectively. The aerodynamic drag changes are negligible with an increase in vehicle separation distance where two vehicles are separated laterally with 1.2 m distance. In all configurations, the leading vehicle aerodynamic drag changes are negligible irrespective of the vehicle separation distance.