In cities around the world, vehicle fires, particularly those involving passenger cars, have become an increasingly common phenomenon. The rising number of motor vehicles and population density in urban areas result in a growing risk of such incidents occurring. Vehicle fires have a significant impact on the urban environment, causing not only physical destruction and threats to human health but also long-lasting ecological consequences.
Due to the danger posed by smoke and high temperatures, the topic of vehicle fires has been extensively discussed. In one of their articles [1] related to tunnel fires, A. Król and M. Król attempted to estimate the number of people at risk in a road tunnel in the event of a fire outbreak. To achieve this, they proposed factors such as traffic intensity, fire location in the tunnel, ventilation system applied in the tunnel, and the possibility of independent evacuation.
In another article [2], the same authors conducted simulations to demonstrate how the number of endangered individuals inside a tunnel changes based on the time of threat detection and reaction to it. The experiment was conducted for a tunnel passing under a river, varying the vehicle type composition immobilized inside the tunnel, the size of the fire, and the timing of ventilation system activation.
The issue of vehicle fires is also highly significant due to its impact on other elements of transportation infrastructure, such as multi-story parking facilities. This solution offers the benefit of space-saving in congested city centres. Fires can influence the durability of concrete structures, as analyzed by Erdélyiová R et al. in one of their articles [3].
Currently, electric vehicles are drawing increasing attention due to globally recognized cases of spontaneous combustion. Extinguishing such fires is complex and time-consuming due to the ongoing process of successive cell heating within the batteries. Analyses related to this subject were presented in another article by M. Król and A. Król [4].
Regarding the impact of fires on urban areas, David J. et al. have already written on this topic. The authors emphasize a specific compound – ammonia – which is also emitted by internal combustion engines of vehicles. Furthermore, the publication discussed the influence of wildfires caused by drought, rather than vehicle fires themselves. It was demonstrated that ammonia emissions impact climate changes in the Colorado area [5].
Automobile production is a rapidly evolving sector of the industry, wherein a key aspect is the selection of appropriate materials for constructing vehicle components and parts. In today's era where fuel efficiency, sustainable development, and safety are paramount, car manufacturers must strike a balance between material strength and weight. Consequently, synthetic materials are finding increasing use. It is estimated that this upward trend will continue. By 2030, the value of the automotive plastics market is projected to exceed $43 trillion, marking a 5.2% growth from 2023 [6, 7].
The ongoing rise in the use of synthetic materials is also attributed to their expanding range of applications. The potential to replace metal components offers benefits such as thermal resistance reaching up to 300 degrees Celsius for selected polymers [8].
Globally, Europe constitutes a significant market in the automotive industry, with a 23.7% share of newly registered vehicles worldwide in 2022 [9]. Therefore, any manufacturer seeking to sell vehicles within the European Union must comply with prevailing regulations and obtain approvals for systems related, among other things, to road safety. This adherence to stringent requirements designed for the European market also ensures the safety of the same vehicles sold in other parts of the world. The implementation of flammability standards for materials used in vehicles is thus a crucial aspect of safety engineering, with the United Nations ECE regulations serving as vital tools in minimizing health risks associated with collisions and vehicle fires.
For instance, Regulation No. 34 of the UNECE deals with vehicle approval for fire protection in the event of a collision, as well as requirements regarding liquid fuel tanks. The regulation outlines methods for conducting impact resistance tests on tanks and the placement of fuel-related components within the vehicle. Moreover, the materials used for fuel tanks must be corrosion-resistant and fire-resistant. The regulation also specifies the pressure values at which each tank must maintain its integrity. Tanks meeting the stipulations of Regulation No. 34 must bear an international approval mark containing the letter “E” and the approval country's number [10].
European regulations also mandate equipping certain vehicles with fire suppression systems located in the engine compartment and other areas housing exhaust heaters. Regulation No. 107 applies to category M2 and M3 vehicles (buses designed to carry more than 8 passengers excluding the driver) and outlines general construction requirements. Information about fire suppression systems in the engine compartment and their operation constitutes only a brief portion of the entire regulation [11].
Another regulation related to fire safety is Regulation No. 118 of the UNECE. Regulation No. 118 focuses on regulating the flammability of materials used inside motor vehicles. This is crucial for safety, as vehicle fires can lead to hazardous situations. The regulation specifies requirements regarding material behaviour under burning conditions, introducing standards for flame resistance, flame propagation, and emission of smoke and toxic gases. By defining flammability criteria, the regulation aims to reduce the risk of rapid fire spread and limit the emission of toxic substances in case of an interior vehicle fire. These standards contribute to improving evacuation conditions, safeguarding drivers, passengers, and those providing assistance during emergencies. However, it's worth noting that Regulation No. 118 only applies to category M3 vehicles – those designed to carry passengers, with more than eight seats besides the driver's seat and a maximum mass exceeding 5 tons [12].
European Union regulations focus on ensuring overall passenger safety in the event of a road incident and ensuring the durability of fuel tanks. However, they do not address the harmfulness of vehicle fires themselves and the quantity of emitted toxic substances into the atmosphere. Legal regulations also do not govern the type and amount of combustible materials used in the production of passenger and commercial vehicles.
Vehicle fires pose a direct threat to the health and lives of residents. Emissions of toxic chemicals and gases can lead to severe respiratory and skin diseases in people exposed to fire smoke. Analyzing the health effects is crucial for assessing the severity of the issue and developing appropriate prevention strategies and crisis management plans. Moreover, vehicle fires release substantial amounts of greenhouse gases and other air pollutants, negatively impacting the air quality in cities. This, in turn, can lead to a reduced quality of life for residents and disrupt the balance of urban ecosystems. Analyzing these effects is essential for understanding the long-term ecological consequences. Vehicle fires also contribute to the generation of hazardous waste, such as burnt plastics and metals. Managing this waste presents a challenge for municipal authorities and waste management institutions. Effective strategies for processing fire-related waste are of utmost importance for minimizing environmental impact [13, 14, 15].
In automotive vehicles, various types of plastics are used, each with specific characteristics and applications. The most significant polymers include polypropylene (PP), polyamide (PA), polyurethane (PUR), polyethylene (PE), acrylonitrile-butadienestyrene (ABS), polyvinyl chloride (PVC), polycarbonate (PC), polyester resins (UP), polyester (PEST), polymethyl methacrylate (PMMA), polybutylene terephthalate (PBT) and rubber, which is a mixture of various elastomers, mainly of polybutadiene (PBD) and polyisoprene (PI) [16, 17, 18]. Table 1 provides examples of vehicle components made from different types of plastics.
Application of selected plastics in passenger vehicles [16, 17, 18]
Element | Plastics used |
---|---|
Bumper | PP, ABS, PC |
Seats | PUR, PP, PCV |
Dashboard | PP, ABS, PA, PC, PE |
Components of the fuel system | PE, POM, PA, PP |
Elements under the hood of the car | PA, PP, PBT |
Car body parts | PP, PPE, UP |
Internal moldings | PP, ABS, PET, POM, PCV |
Electrical components | PP, PE, PBT, PA, PCV |
Headlights | PP, PC, ABS, PMMA, UP |
Upholstery | PCV, PUR, PP, PE |
External mouldings | ABS, PC, PBT, ASA, PP |
Tyres | Rubber (PBD, PI) |
Others | PP, PE, PA |
It is estimated that for an average passenger vehicle in the United States with a mass of 1950 kg, approximately 186 kg are comprised of elements made from plastics and polymer composites. This accounts for 9.6% of the vehicle's own mass, primarily consisting of 44 kg of polypropylene (PP), 38.1 kg of polyurethane foam (PUR), 18.6 kg of nylon (PA), 15.4 kg of high-density polyethylene (HDPE), and 14.1 kg of polyvinyl chloride (PVC) [19]. The aforementioned general mass of plastics also includes rubber, which is the basic component of tires (approx. 80%) [20]. The average mass of a tire with a diameter between 16 and 17 inches is about 10 kg [21], so the share of rubber in the tires of an average four-wheeled vehicle may amount to 36 kg.
Assuming that the average mass of a European passenger vehicle is 1385 kg [22], a truck is 12,250 kg [23], a bus is 10,400 kg [24], and an average motor-powered two-wheeler is 180 kg [25], it is possible to roughly estimate the amounts of plastics in other types of vehicles using proportions. The quoted values are masses of different types of representative vehicles in Europe adopted for further calculations. Table 2 presents an overview of calculated and approximate masses of selected plastics used in the construction of various types of transportation.
Approximate plastic masses for different vehicle types
Type of plastic | The mass of plastics in a given type of vehicle [kg] | |||
---|---|---|---|---|
Passenger vehicle | Truck | Bus | Two-wheeler | |
PP | 31.2 | 276.4 | 234.7 | 4.1 |
PUR | 27.1 | 239.3 | 203.2 | 3.5 |
PA | 13.2 | 116.8 | 99.2 | 1.7 |
HDPE | 10.9 | 96.7 | 82.1 | 1.4 |
PVC | 10.0 | 88.6 | 75.2 | 1.3 |
Rubber | 26.6 | 226.2 | 192.0 | 3.3 |
As mentioned in the previous section of the article, plastics are a significant material in various industries, including the automotive sector. However, their flammability can pose certain hazards. In case of accidents or incidents leading to a fire, the presence of combustible plastics inside a vehicle can accelerate the spread of fire and generate toxic gases. Highly flammable plastics, such as polyurethane foams or certain types of polypropylenes, can release toxic substances during combustion, endangering the health of individuals inside the vehicle as well as rescue personnel. Additionally, the process of plastic combustion can rapidly weaken the vehicle's structure, hindering evacuation and rescue efforts.
The amount of substances generated during combustion depends on various factors, primarily combustion temperature and the amount of available oxygen. Real-world fires, not only in vehicles but also in buildings, are unpredictable, thus precise determination of combustion products is not possible. True fires are not conducted under repeatable laboratory conditions, which is why approximations of combustion product quantities are used in the article. Given the complexity of the combustion process, laboratory-perfect pollution levels are unattainable. Combustion products of selected polymers along with their approximate masses of selected pollutants are presented in Table 3.
Combustion products of selected polymers along with approximate masses of selected pollutants [26, 27, 28, 29]
The type of pollution | Approximate mass of combustion product in relation to 1 kg of material mass [g/kg] | |||||
---|---|---|---|---|---|---|
PP* | PUR | PA | HDPE | PVC | Rubber | |
Benzene | 0.90 | 5.00 | 5.00 | 2.00 | X | X |
Toluene | 0.26 | 0.46 | 0.50 | 0.26 | X | X |
Formaldehyde | 1.16 | 0.93 | 0.25 | 1.16 | X | X |
Acetaldehyde | 1.45 | 1.21 | 0.19 | 1.45 | X | X |
Phenol | 0.03 | 0.43 | 0.01 | 0.03 | X | X |
Benzoic acid | 0.20 | 7.65 | 0.32 | 0.21 | X | X |
Sulfur dioxide | X | X | X | X | X | 20.0 |
Nitrogen oxide | X | X | X | X | X | 2.50 |
Hydrogen chloride | X | X | X | X | 250 | 11 |
Hydrogen cyanide | X | 2.00 | 2.00 | 1.00 | X | X |
Warsaw is the largest city and the capital of Poland, with a population of 1,863,056 people residing in an area of 517.2 km2, resulting in a population density of approximately 3,602 people/km2 according to 2022 data [30]. Warsaw serves as a significant financial and business hub in Central and Eastern Europe, experiencing a growing population year by year. Under the current administrative division, Warsaw is divided into 18 districts. Table 4 provides information about the area, population, and population density of each district in Warsaw.
Basic demographic information about the districts of Warsaw [30]
District | Number of residents | Area [km2] | The density of population [pers./km2] |
---|---|---|---|
Bemowo | 129169 | 24.95 | 5177 |
Białołęka | 153100 | 73.00 | 2096 |
Bielany | 133478 | 32.34 | 4127 |
Mokotów | 225916 | 35.42 | 6378 |
Ochota | 80988 | 9.72 | 8332 |
Praga-Południe | 186834 | 22.38 | 8348 |
Praga-Północ | 60855 | 11.31 | 5381 |
Rembertów | 24670 | 19.30 | 1278 |
Śródmieście | 101979 | 15.57 | 6550 |
Targówek | 124240 | 24.33 | 5106 |
Ursus | 67373 | 9.35 | 7198 |
Ursynów | 151432 | 43.79 | 3458 |
Wawer | 86399 | 79.71 | 1084 |
Wesoła | 26380 | 22.94 | 1150 |
Wilanów | 51172 | 36.73 | 1393 |
Włochy | 49280 | 28.63 | 1721 |
Wola | 151158 | 19.26 | 7848 |
Żoliborz | 58633 | 8.47 | 6922 |
Through Warsaw flows the Vistula River, the longest river in Poland, dividing the city into two sides – the northeastern and the southwestern. Figure 1 illustrates the administrative division of Warsaw, taking into account the population density of individual districts, along with the Vistula River flowing through the city.
Thanks to the cooperation of the management of the Municipal Headquarters of the State Fire Service, data concerning vehicle fires in the capital city of Warsaw has been made available. The data, obtained from the Municipal Headquarters of the State Fire Service in Warsaw, includes the number of interventions by the State Fire Service due to vehicle fires in the period from January 1, 2010, to April 30, 2021, within the city of Warsaw.
The data was provided in the form of spreadsheets with filled cells. Vehicle fires were categorized into four groups: buses and trolleybuses, motorcycles and mopeds, trucks, and passenger vehicles. Each intervention, in addition to the date and time of the incident, includes a brief description of the burning vehicle, the street of the incident, and the geographic coordinates of the fire. Based on these coordinates, it was possible to conduct an analysis of city areas exposed to harmful substances resulting from vehicle fires.
The data was analyzed for accuracy. All errors were identified during spatial analysis and corrected accordingly. Most mistakes involved incorrectly determined fire locations, which were detected through repeated coordinates associated with different addresses.
Based on the number and locations of fires, it was possible to calculate the amount of emitted substances in specific districts of Warsaw. Furthermore, by dividing the emissions of pollutants by the population of each district, it was possible to estimate how much approximately toxic substances were emitted per resident due to vehicle fires.
The results of the analysis were presented using Quantum GIS (QGIS) software, which enables the creation, editing, analysis, visualization, and management of spatial data. This software is utilized in spatial analysis, urban planning, geographic studies, and scientific research where spatial information plays a crucial role.
Comparing vehicle fires for trucks is uneven, as much depends on the type of cargo being transported. Therefore, a dump truck loaded with sand to the brim presents less risk than a delivery vehicle carrying tires, flour, or paints.
Figures 2, 3, 4, and 5 respectively depict the locations of fires on a map of Warsaw, considering the population density in each district.
Based on the data obtained from the fire brigade, it was possible to analyze the number of fires that occurred in each district of Warsaw. Table 5 provides information on the number of vehicle fires in the districts of Warsaw, categorized by the type of burning vehicle.
Vehicle fires in Warsaw, categorized by districts and type of burning vehicle
District | Number of vehicle fires | |||
---|---|---|---|---|
Passenger vehicles | Trucks | Buses | Two-wheelers | |
Bemowo | 152 | 13 | 1 | 3 |
Białołęka | 220 | 29 | 19 | 5 |
Bielany | 162 | 14 | 9 | 6 |
Mokotów | 378 | 34 | 8 | 9 |
Ochota | 171 | 5 | 3 | 2 |
Praga-Południe | 307 | 13 | 4 | 5 |
Praga-Północ | 191 | 14 | 7 | 6 |
Rembertów | 74 | 16 | 2 | 0 |
Śródmieście | 270 | 20 | 10 | 5 |
Targówek | 284 | 28 | 9 | 4 |
Ursus | 89 | 11 | 4 | 2 |
Ursynów | 239 | 19 | 8 | 4 |
Wawer | 232 | 31 | 6 | 1 |
Wesoła | 56 | 6 | 1 | 0 |
Wilanów | 74 | 5 | 1 | 0 |
Włochy | 155 | 16 | 6 | 1 |
Wola | 233 | 26 | 7 | 7 |
Żoliborz | 112 | 16 | 0 | 1 |
Warsaw | 3399 | 316 | 105 | 61 |
The acquired data was subjected to further analysis. Based on the information provided in section 2.3., it is possible to calculate the total amount of pollutants (without distinguishing individual chemical compounds) generated as a result of vehicle fires. For this purpose, the following relationship can be used:
TP – total pollutants, kg Mn – mass of polymer in the vehicle, where n is the type of polymer analyzed, kg Pn – the amount of harmful substances generated by burning 1 kg of polymer, where n is the type of analyzed polymer, g/kg
By multiplying the obtained result for a single vehicle by the number of vehicle fires, it is possible to calculate the total amount of pollutants generated from all the fires recorded by the fire brigade. This calculation can be performed for each type of vehicle. Additionally, after dividing the calculated total pollutants by the population of each district, it was possible to obtain the average pollution per resident in each district of Warsaw. Calculating such a value required using the relationship provided below:
AP – average pollutants, kg/km2 FV – number of vehicle fires AD – area of district, km2
The results of calculations using the two provided formulas for Warsaw districts are presented in Table 6.
Estimated total quantities of toxic substances emitted due to vehicle fires in Warsaw from 2010 to 2021, categorized by districts, along with the amount of average pollutants per year and per square kilometer
District | Amount of toxic substances emitted by vehicle fires [kg] | Total pollutants [kg] | Average annual pollutants [kg] | Average pollutants on the area [kg/km2] | |||
---|---|---|---|---|---|---|---|
Passenger vehicle | Truck | Bus | Two-wheeler | ||||
Bemowo | 629.24 | 476.00 | 31.09 | 1.61 | 1137.94 | 110.12 | 45.61 |
Białołęka | 910.74 | 1061.84 | 590.62 | 2.69 | 2565.90 | 248.31 | 35.15 |
Bielany | 670.64 | 512.61 | 279.77 | 3.23 | 1466.25 | 141.89 | 45.34 |
Mokotów | 1564.82 | 1244.91 | 248.68 | 4.84 | 3063.26 | 296.44 | 86.48 |
Ochota | 707.90 | 183.08 | 93.26 | 1.08 | 985.30 | 95.35 | 101.37 |
Praga-Południe | 1270.90 | 476.00 | 124.34 | 2.69 | 1873.93 | 181.35 | 83.73 |
Praga-Północ | 790.69 | 512.61 | 217.60 | 3.23 | 1524.13 | 147.50 | 134.76 |
Rembertów | 306.34 | 585.84 | 62.17 | 0.00 | 954.35 | 92.36 | 49.45 |
Śródmieście | 1117.73 | 732.30 | 310.85 | 2.69 | 2163.58 | 209.38 | 138.96 |
Targówek | 1175.69 | 1025.22 | 279.77 | 2.15 | 2482.83 | 240.27 | 102.05 |
Ursus | 368.44 | 402.77 | 124.34 | 1.08 | 896.62 | 86.77 | 95.90 |
Ursynów | 989.40 | 695.69 | 248.68 | 2.15 | 1935.92 | 187.35 | 44.21 |
Wawer | 960.42 | 1135.07 | 186.51 | 0.54 | 2282.54 | 220.89 | 28.64 |
Wesoła | 231.83 | 219.69 | 31.09 | 0.00 | 482.60 | 46.70 | 21.04 |
Wilanów | 306.34 | 183.08 | 31.09 | 0.00 | 520.50 | 50.37 | 14.17 |
Włochy | 641.66 | 585.84 | 186.51 | 0.54 | 1414.55 | 136.89 | 49.41 |
Wola | 964.56 | 951.99 | 217.60 | 3.77 | 2137.92 | 206.90 | 111.00 |
Żoliborz | 463.65 | 585.84 | 0.00 | 0.54 | 1050.03 | 101.62 | 123.97 |
Warsaw | 14071.00 | 11570.37 | 3263.97 | 32.82 | 28938.16 | 2800.47 | 55.95 |
The highest number of fires and consequently the greatest cumulative pollution were recorded in the Mokotów district. However, when calculated per square kilometer, the most polluted districts due to fires were Śródmieście, Praga-Północ, Żoliborz, Wola, Targówek and Ochota. In these six districts, fires generated over 100 kg of pollutants per square kilometer, whereas the average pollution for the entire city of Warsaw was 55.95 kg/km2. The high number of fires may be related to streets with high traffic volumes running through these districts or deliberate vehicle arsons as a result of vandalism.
On the other hand, residents of Wesoła and Wilanów experienced the least pollution. These are areas with large surface areas and low population densities, further away from the city center and therefore with fewer vehicles.
The presented results are an attempt to estimate the impact of vehicle fires on the urban environment. The analysis did not consider the influence of wind on the movement of toxic substances from one district to another. There is also no information on how much the given vehicles burned; for the purposes of the article, it was assumed that they burned completely, but some vehicles may have been extinguished before complete combustion. Additionally, it is not possible to precisely determine the amount of substances, as it depends on factors such as combustion temperature and oxygen supply, as mentioned in the section on materials used in vehicles. Each individual fire case is unique in its own way. Further research will be needed in this area due to the complexity of fire-related issues and the increasing percentage of electric vehicles, whose extinguishing is hindered due to electric batteries.
According to the presented research findings, the development of the automotive industry may also entail negative effects. While the increasing use of lightweight materials based on plastics results in energy savings required for transportation, there remains the challenge of disposing of such materials once they are no longer needed.
As demonstrated in the article, an even worse scenario involves fires involving synthetic materials, during which harmful substances are emitted. The quantity of these substances depends directly on the type of vehicle and any potential cargo, especially in the case of heavy-duty vehicles. The impact of such incidents on urban environments is detrimental, as they can lead to health issues for individuals exposed to the smoke emitted from the fire.
City authorities possess several means to enhance road traffic safety, such as implementing maximum speed limits on specific road segments, improving road infrastructure quality, or advancing intelligent transportation systems along with modifications in areas most susceptible to collisions.
Reducing the number of road collisions should be the foremost objective, positively influencing road traffic safety, as well as minimizing vehicle fires within urban areas. Moreover, the number of road-related events that could lead to fires can be decreased through regular vehicle servicing and maintenance, as well as heightened supervision over periodic vehicle inspections.
Education about road safety is also of significance, coupled with refining vehicle operation skills. Similarly, elevating the level of safety and prompt detection of acts of vandalism will contribute to fewer deliberate vehicle arsons.
Data collected by the fire department concerning vehicle fires do not always precisely determine the extent of the threat. A greater level of detail regarding the cargoes carried by heavy-duty vehicles would enable a precise calculation of fire intensity and consequently the amount of generated pollutants. Implementation of internal data collection procedures within the fire department would prove beneficial for future analyses.
At present, materials that combine the advantages of existing materials while remaining environmentally neutral do not exist. An ideal material would need to possess high tensile strength, be resistant to high temperatures, have low mass while being inexpensive, and also be capable of reusability.