A Systematic Study on the Analysis of the Emission of CO, CO 2 and HC for Four-Wheelers and Its Impact on the Sustainable Ecosystem

: The urbanization in Delhi NCR has led to a rapid increase in the vehicle count concerning the rise in population and mobilization. The emissions from the vehicles are currently counted amongst the main sources of air pollution in Delhi. This a ﬀ ects the quality of air. The emission criterion of various pollutants that are emitted from vehicles is evaluated through various International models, which include various vehicles, their modes of pollutants emitted while driving and other factors that are a ﬀ ecting the weather. The approximate emission of pollutants such as Carbon Monoxide (CO) and / or Particulate Matter (PM), from a variety of vehicles and di ﬀ erent fuel types, has undergone diurnal variation over the years, depending on the time of the day. This study presents the emission factor of gaseous pollutants Hydrocarbons (HC), Carbon Monoxides (CO) and Carbon Dioxide (CO 2 ) of 181 four-wheeler cars from di ﬀ erent companies containing di ﬀ erent types of fuels. The measurement of gaseous pollutants is performed for Delhi, the most polluted city in India. The various facts and data were calculated and analyzed with reference to the standard values set by the national schemes of the Pollution and Environment. Based on this statistical data obtained and analyzed, the scenarios regarding future vehicle growth rate and its impact on air quality are mentioned to overcome emission problems. Therefore, it is important to develop and deploy methods for obtaining real-world measurements of vehicle emissions, to estimate the pollutants. The analysis shows that few parameters need to be a concern for reducing the pollutants emission by vehicles. These major parameters are the high survival rates, decrease in annual mileage and major enforcement for three-to-ﬁve-year-old vehicles. This study shows that many old vehicles are used in di ﬀ erent regions of the country, regardless of many notiﬁcations of banning old vehicles by the Government of India. These old vehicles are the major source of vehicle pollutants. The analysis stated that the diesel engine would emit less CO 2 / km than a petrol engine if having an almost similar engine capacity.


Introduction
India is one of the biggest emitters of pollutants, and vehicle pollution is one of the major sources of these pollutants. Here we present an inventory of vehicle pollution for different car models and companies. This inventory is the study of major pollutants Hydrocarbons (HC), Particulate Matter (PM), Carbon Monoxides (CO) and Carbon Dioxide (CO 2 ), for the period from 2005 to 2019. These inventories play a very important role when we discuss the input for modeling of atmospheric composition, about the air and other pollution. In this paper, we study the major makers/companies of four-wheelers vehicles that emit the pollutants in the air. The maker/companies considered for this study are Toyota, Maruti Suzuki, Hyundai, Honda, Mahindra, TATA and some other luxury makers.
According to WHO, air pollution kills around seven million people worldwide every year. The data show that approximately 90% of the population breathes air containing high levels of pollution, resulting in around seven million deaths every year due to such exposure. In January 2019, the state-run Central Pollution Control Board's air-quality index shows that the concentration of poisonous Particulate Matter, also known PM 2.5, stood at 440 and about 12 times more than the US-government-recommended level, i.e., the level of 35. Therefore, it becomes imperative for us to deeply understand and analyze the causes of air pollution in our surroundings. Vehicles are one of the major sources of emission of pollutants, especially in urban areas. The major pollutants associated with vehicular emission are Hydrocarbons (HC), Particulate Matter (PM), Carbon Monoxides (CO) and Carbon Dioxide (CO 2 ). In this paper, we analyze these major pollutants emitted by different fuel vehicles. In the next section, we detail these pollutants in brief. The fuel and air can be the source of different pollutants that can be harmful to human health. Here we discuss some of the major pollutants caused by vehicular emission.
Hydrocarbons (HC) are considered to be specks of molecules of fuel that are not fully burned. These react when sunlight and oxides of Nitrogen are present, and the reaction results in the formation of ground-based ozone. The ozone so formed majorly contributes to smog and irritates the eyes and nose and also damages the lungs. Some exhausts' HCs are harmful, too, with the potential to cause cancer. Carbon Monoxide (CO) is the product of the incomplete burning of Hydrocarbons-based fuels. It is a colorless, odorless and poisonous gas. Mostly, when cars are about to start, and if they are not tuned in a proper way or at higher altitudes, where the fraction of oxygen that is available for combustion decreases, then the CO formed has a low air-to-fuel ratio in the engine. Two-thirds of the CO emissions arise from the sources of transport, cars being the largest contributor. In some areas, the contribution of on-road vehicles to Carbon Monoxide pollution may rise up to 90%. The affinity of CO to hemoglobin is about 250 times more than the oxygen. This may cause mild-to-severe poisoning, depending upon the concentration of CO and its exposed length. The symptoms include headache, dizziness, nausea, vomiting and loss of consciousness. Carbon Dioxide (CO 2 ), as per the US Environmental Protection Agency (EPA), initially inspected CO 2 as a result of "complete" combustion, but now suspects Carbon Dioxide as the concern of pollution. CO 2 is a greenhouse gas that traps the heat of the earth and contributes to the change in the climate.
We have seen that the new vehicles are comparatively less polluting than before, but the number of vehicles and the overall distances traveled by them has considerably increased, and the people, especially while commuting, are heavily exposed to such pollutants. One such region which has an air-quality level of criticism is the Delhi National Capital Region. Delhi, also being the capital, is undergoing rapid development, with an ever-increasing number of vehicles, reaching more than 10 million now. Delhi NCR has been given the worst position among the 14 major cities of the country, on the basis of vehicular emissions, according to a study conducted by the Centre for Science and Environment (CSE). A survey conducted by IIT-Kanpur has revealed that such emissions from vehicles contribute 9% of the total Particulate Matter 10 (PM10) and 20% of the total PM2.5 in the national capital. Recently there have been some initiatives taken to curb or reduce vehicular pollution, Sustainability 2020, 12, 6707 3 of 22 including public-awareness campaigns, registration of only those first-sale four-wheeled petrol-driven vehicles which have catalytic converters installed, the expansion of the rapid public transport system, the phasing out of old commercial vehicles, compliance of tightened emission standards and improvement in fuel quality by completely phasing out leaded petrol, and introduction to low Sulfur diesel. However, despite all of these measures taken, the problem still persists, and there is a large and excessive need for studies and analyses, to understand the problem at a deeper level, and with those results, a more practical approach can be strategized. Hence, our paper analyses the different types of pollutants emitting from distinct vehicles, at different periods of time, and gives an overall view of the most current situation in this region.
Timely differences in vehicle emissions are influenced by many inter-mixing factors in the real world. Post tailpipe emission the particles go through a change as they come into the contact with atmosphere, as observed when we see two times the increase in emission factors from summer to winter [1]. Taking cost-effectiveness into account is one of the major things when it comes to implementing policies for the reduction of vehicular emissions. It was seen that implementing a policy of limited driving was less cost-effective than a policy of elimination of old cars [2]. Pollutants such as SO 2 , HC, CO 2 , CO and PM are emitted by vehicles in very high quantities [3]. Detailed specifications of the compound of gases where the particles are studied at different stages, such as cooling, equilibrating to current conditions, are needed for the evaluation of vehicular emissions [4][5][6]. Usually, the estimation of vehicular and engine emissions is done by using a chassis dynamometer and engine, but these are costly and require quite a high amount without the representation of real-life emissions [6]. Tunnel studies and remote sensing aptly represent the road fleet emissions, but traffic flow, road conditions and technology lead to varying real-life emissions [7,8].
Certain studies have been conducted for the evaluation of pollutant emission from Particulate Matter and gaseous pollutants [9].However, mostly, these evaluations are carried out for a few specific developing countries only. Intergovernmental Panel on Climate Change (IPCC) (2007) states that activity data and emission profiles from a regional source are required for the calculation of tier-two emissions. A large dataset is required for the refined estimation of emission from the road transport sector, while encompassing the effects of all the region-specific variables.
The indoor air quality has been measured by the emission evolution of specific indoor sources. This procedure included three typical activities, namely cooking style, biofuels and different levels of toasting bread [10]. In another study [11], three different models were integrated into a hybrid model for the prediction of vehicular emission, at a specific location and time, in Malaysia. A method has been proposed for emission estimation and energy consumption based on the condition of vehicles in different regions such as Spain, Malaysia and Colombia [12]. In another study, the author discussed the delay issues and time complexity on the internet of vehicles [13]. The prediction of boiler performance in terms of mass flow rate and the temperature was performed by using Artificial Neural Networks (ANNs) [14,15].
An inventory was performed for the Bangaluru region at a grid resolution of 1 km [16]. Another study provides the PM10 and PM2.5 concentration data for a populated region in Erongo [17]. The properties of SO 2 adsorption have been explored and evaluated [18]. Another study investigated the combustion and emission characteristics of diesel engines [19].
Strict vehicle emission regulations make sure that vehicles are efficient during their operation [20]. For major vehicle categories, the emission limits from the late 1990s are given by Euro Path; in 2000, 2004 and 2007, they were given by National-1, N-2 and N-3 standards. However, while implementing N-3 standards, it has been observed that the vehicle degradation occurs as the vehicle emission factors reach their highest values (Zhang et al., 2008). Hence, it was seen that, only after enforcing the N-4 standards, the pollutant emission factor was decreased [20]. Findings from the American Environment Protection Agency showed that NO x emission was decreased by 5%, HC emission was decreased by 7% and CO emission was decreased by 8% when the Sulfur (S) content in fuel was decreased to Sustainability 2020, 12, 6707 4 of 22 49 mg/kg, which was almost similar to the N-4 fuel standard from 327 mg/kg, which was similar to N-3 fuel standard.
In Delhi, the road traffic increased from 128 to 191 vehicles per kilometer in the time frame from 2003 to 2009 [21]. Due to this, the availability of road space in Delhi increased by 678 lane kilometers between 2003 and 2009. In Delhi, the average annual rate of the vehicle population growth is about 9.150% for commercial and 7.40% for private vehicles. Annual growth in the vehicle population is causing severe environmental problems in Delhi [22]. Delhi occupies the fifth position when it comes to the worst traffic congestion/jams in a major city. Various models, like Spreadsheet, Long-Range Energy Alternative Planning (LEAP) and Vehicle Air Pollution Information System (VAPIS), do not take into consideration many distinguishing factors in the local environment, such as management of traffic and behavior of the driver; along with this, there is also an assumption that vehicles having lower speed increase the pollutant emission. Considering the above discussion, an IVE model which has been applied in various major cities all over the world, including cities such as Shanghai and Beijing in China, can be used for emission estimations [23]. For differently fueled vehicles, features such as meteorological variables, emission factors and different modes of driving are being used in this model, with further related studies in References .
The study by Reference [55] concentrated on the analysis of CO 2 emission for five NMI subsectors. Authors have studied the CO 2 emission for the time period of 30 years, from 2010 to 2030. In another study, authors have estimated the environmental technical efficiency and shadow prices for SO 2 emissions of China's provinces, from 2001 to 2013 [56]. Authors have highlighted the incompatibility in Carbon neutrality assumptions, system boundaries, methodologies and functional units in LCA studies of paper and pulp making [57]. An analysis has also been carried out which measures the effect of acceleration and speed on the emission of HC, CO and NOX in four-stroke motorcycle exhaust [58]. Another study has discussed the prospect of ethanol as an effective substitute for gasoline and also analyzed its effect on the emissive behavior of SI engines [59].
Some initiatives have been already taken to curb or reduce vehicular pollution: public awareness campaigns, registration of only those first-sale four-wheeled petrol-driven vehicles which have catalytic converters installed, the expansion of the rapid public transport system, the phasing out of old commercial vehicles, the compliance of tightened emission standards and improvement in fuel quality by completely phasing out leaded petrol and introduction of low Sulfur diesel. However, despite all of these measures taken, the problem still persists as a large and excessive need to study this situation, and analyses are required to understand the problem at a deeper level; with those results, a more practical approach can be strategized. This study shows that few parameters need to be a concern for reducing the pollutants emission by vehicles. These major parameters are the high survival rates, decrease in annual mileage and major enforcement for three-to-five-years-old vehicles. This study shows that many old vehicles are used in different regions after the many notifications regarding banning old vehicles by the Government of India. These old vehicles are the major source of vehicle pollutants.
The urbanization in Delhi NCR has led to a rapid increase in the vehicle count with respect to the rise in population and mobilization. The emissions from the vehicles are currently counted amongst the main sources of air pollution in Delhi, and this affects the quality of air. The emission criterion of various pollutants that are emitted from vehicles is evaluated through various international models that include the different vehicles, their driving modes, pollutants emitted and other meteorological factors. The estimated emissions of pollutants such Carbon Monoxide (CO) and Particulate Matter (PM) from different types of vehicles and different fuel types have undergone diurnal variation over the years, depending upon the time of the day. This paper makes an attempt to study and analyze the pollutants by the emission of gases by vehicles which emit from them. The various facts and data were calculated and analyzed with reference to the standard values set by the national schemes of pollution and the environment. Based on this statistical data obtained and analyzed, the scenarios regarding future vehicle growth rate and its impact on air quality are mentioned, to overcome emission problems. Therefore, it is important to develop and deploy methods for obtaining real-world measurements of vehicle emissions, to estimate the pollutants. The comprehensive review reveals whether the moving vehicles create a significant impact on air quality on specific locations or not.
The significant contribution of this paper is its presentation of the gaseous pollutants (Hydrocarbons (HC), Carbon Monoxides (CO) and Carbon Dioxide (CO 2 )) emission factor of 181 four-wheeler cars from different companies and of different types of fuels. Based on this statistical data obtained and analyzed, the scenarios regarding future vehicle growth rate and its impact on air quality are mentioned, to overcome emission problems. This study shows that many old vehicles are used in different regions, even after the many notifications regarding banning old vehicles by the Government of India. These old vehicles are the major source of vehicle pollutants. The unauthorized installation of compressed natural gas (CNG) kits also has to be banned strictly. Secondly, technological advancement not only targets fuel efficiency but also targets the reduction of CO, CO 2 and HC. It will be helpful to pollution-monitoring authorities for making new and effective policies against the emission of pollutants by vehicles.
The paper is organized as follows: The methodology is discussed in Section 2, which includes the quantification of emissions, studied area, experimental setup and data collection; Section 3 presents the result analysis; and, finally, the study is concluded in Section 4.

Quantification of Emissions
The estimation of the emissions from the on-road vehicles is done on the basis of a number of vehicles and distance traveled in a particular year per different vehicle. This can be expressed as follows: where Ei = emission of compound (i); Vehj = number of vehicles per type (j); Dj = distance traveled in a year per different vehicle type (j); and Ei,j, and km = emission of compound (i) from bottom-up approach [60] were taken into account so as to estimate gaseous and particulate emission based on annual average utilization for a different vehicle category, number of registered vehicles and the corresponding emission factors vehicle type (j) per driven kilometer. Annual utilization of cars and jeeps and taxi were assumed to be 33,500, 12,600 and 12,600 km, respectively. These values were taken on the basis of five-year planning reports of India. For other sections of vehicles, annual utilization was calculated by taking the average of all the above values. The CO 2 emission [61] is estimated by using the value of the consumption of fuel [24,62] and emission factor, as follows: where Ei = emission of compound (i); Fuel j,k = consumption of fuel (j) for transport type (k); and EFi,j= emission factor for compound (i) emitted from fuel (j). Emissions of CO and HC were estimated by using the following equation: Stoichiometric air-fuel ratio and equivalence air-fuel ratio or Lambda(λ) are the important parameters for the analysis of pollution emitted by vehicles. To understand the Stoichiometric air-fuel ratio, we need to look at the fuel combustion process. It is a process in which the mixture of fuel and water produces water, heat and Carbon Dioxide. Activation energy is also required for the occurrence of such an oxidation reaction. With the help of Stoichiometric air-fuel ratio, the value of Lambda can be calculated by using the following equation: Hence, the Lambda factor can be calculated by using the actual and ideal value of air-fuel ratio.

Locations
The most appropriate region chosen for the analysis of vehicular emission and its pollutants is the Delhi Northern Central Region. Delhi, a vast metropolitan area in the northern part of the country, is India's capital territory as shown in Figure 1. The city covers the area of 1484 square kilometers (573 sq. mi) bordered by Haryana and Uttar Pradesh. The urban area of Delhi extends afar from the national capital territory border. The National Capital Region (NCR) consists of cities like Gurgaon, Noida, Ghaziabad and Faridabad. The National Capital Region (NCR) also includes Delhi, which is considered to be an"interstate regional planning" area by the National Capital Region Planning Board Act of 1985. A survey conducted by the World Health Organization (WHO) in 2014 shows that Delhi was the most polluted city in the world. Delhi was downgraded to the eleventh-worst city in the urban air-quality database in 2016. The air quality of Delhi is usually Moderate (101-200) level between January to September, and then it becomes Very Poor (301-400), Severe (401-500) or Hazardous (500+) between October and December. There is such deterioration in air quality due to various factors like stubble burning, firecrackers burning during festivals like Diwali and cold weather. The levels of Particulate Matter (PM) in Delhi have increased by about 44%, mainly due to high industrial and vehicular emissions, construction work and crop burning in neighboring states. The level of airborne Particulate Matter is also very high, that is, around PM 2.5, which is considered as most harmful to health. Increasing levels of vehicular pollution have consequently caused diseases such as asthma and lung cancer amongst the population of Delhi. The dense smog results in major air and rail traffic disruptions every year, during the winter season. The Indian meteorologists lately stated that the average peak temperature during winters has decreased in Delhi since 1998 due to rising vehicular emissions and, hence, the air pollution. Some measures have been taken to overcome air pollution in Delhi. Delhi has been ranked third amongst the other Indian cities in the count of trees. The world's largest fleet of eco-friendly compressed natural gas (CNG) buses is controlled by Transport Cooperation of Delhi. The CSE began public interest litigation that ordered the Delhi's transport system to switch on CNG and not to use the leaded petrol in 1998. The Department of Energy of the United States declared Delhi as its first "Clean Cities International Partner of the Year" in 2003 for its efforts to overcome air pollution by choosing eco-friendly fuel initiatives. The air pollutants in the city are also reduced by choosing Delhi metro cooperation as the main transport source in the city. Therefore, as per various studies, many of the gains are lost. There's a significant decrement in bus ridership due to an increment in the market share of diesel cars. The city remains assessed at basic sustainability due to the Carbon emissions of its poorer neighborhoods. Therefore, as per various studies, many of the gains are lost. There's a significant decrement in bus ridership due to an increment in the market share of diesel cars. The city remains assessed at basic sustainability due to the Carbon emissions of its poorer neighborhoods.

Experimental Setup
In this section, we discuss the test procedure used for analyzer gasses. Some of the compulsory steps needed to be performed for the analysis of gas. For the gas analyzer, as per the specifications of the fabricator, the power supply is checked, and earthing also needs to be proper,in order to perform a test on vehicles. The electrical calibration should be checked. The availability and the functionality of all the components as per the fabricator need to be checked. With the help of the sample gas of suitable value for Carbon Monoxide (CO) and Hydrocarbons (HC), the span and zero calibrations are checked. We also need to check if the sampling system is leak-proof or not. Finally, it is checked if the printer is working efficiently and the print-out information is correct.
We also discuss the test procedure used for smoke meters. Some of the necessary steps needed to be carried out on smoke meters. It is checked that if the calibration of the meter is at zero and midscale point while the neutral density filter is available, after the warm-up of the meter. The ideal value must lie within 0.1 m −1 . The components, such as the sample hose, internal pipes, etc., are checked if they are deteriorated or have damages, to ensure that there are no leakages. The functionality of the heating system for the optical chamber is checked. The purge air system and visual displays should also be checked, to see if they are working correctly. The functioning of the oil temperature and Revolutions Per Minute (RPM) sensor also needs to be checked. Finally, it is checked if the printer is working efficiently and the print out information is correct, and the instrument casing should be proper, with a proper electrical earthling.
The prescribed standard for different fuel-type vehicles consists of the appropriate values of Carbon monoxide (CO), Hydrocarbon (HC) and Lambda in the different Bharat stage norms as shown in Table 1. Here, CO and HC have emitted pollutants, and Lambda indicates the optimum

Experimental Setup
In this section, we discuss the test procedure used for analyzer gasses. Some of the compulsory steps needed to be performed for the analysis of gas. For the gas analyzer, as per the specifications of the fabricator, the power supply is checked, and earthing also needs to be proper, in order to perform a test on vehicles. The electrical calibration should be checked. The availability and the functionality of all the components as per the fabricator need to be checked. With the help of the sample gas of suitable value for Carbon Monoxide (CO) and Hydrocarbons (HC), the span and zero calibrations are checked. We also need to check if the sampling system is leak-proof or not. Finally, it is checked if the printer is working efficiently and the print-out information is correct.
We also discuss the test procedure used for smoke meters. Some of the necessary steps needed to be carried out on smoke meters. It is checked that if the calibration of the meter is at zero and midscale point while the neutral density filter is available, after the warm-up of the meter. The ideal value must lie within 0.1 m −1 . The components, such as the sample hose, internal pipes, etc., are checked if they are deteriorated or have damages, to ensure that there are no leakages. The functionality of the heating system for the optical chamber is checked. The purge air system and visual displays should also be checked, to see if they are working correctly. The functioning of the oil temperature and Revolutions Per Minute (RPM) sensor also needs to be checked. Finally, it is checked if the printer is working efficiently and the print out information is correct, and the instrument casing should be proper, with a proper electrical earthling.
The prescribed standard for different fuel-type vehicles consists of the appropriate values of Carbon monoxide (CO), Hydrocarbon (HC) and Lambda in the different Bharat stage norms as shown in Table 1

Data Collection
The following data were collected from pollution certificate centers of Delhi NCR. A total data of 181 vehicles were used and analyzed collectively, to reach the following outcomes. Table 2 showcases the characteristics of the different vehicles which were analyzed by displaying varying vehicle maker/companies having different models and registration dates. It also shows the varying or similar engine capacities between two fuel types (diesel and petrol) from different vehicle models. Engine capacity of a vehicle simply depicts the area in which any engine's pistons work/operate; hence, a larger amount of fuel and air is being processed when a vehicle is moving with a larger engine capacity. The average engine capacity calculated from the given table is 1778 cm 3 (approximately) for diesel engines and 1295 cm 3 (approximately) for petrol engines; hence, we can observe that vehicles having a diesel engine have a larger engine capacity, on average, than vehicles having a petrol engine, meaning that it is processing more fuel than its counterpart. A major difference between diesel and petrol engines is that the diesel engine uses more air and less fuel than the petrol engine to operate at the same level, hence emitting less CO 2 despite having a larger concentration of Carbon in it than petrol. The analysis stated that the diesel engine would emit less CO 2 /km than a petrol engine if having an almost-similar engine capacity.  Tables 3-5 display the value/level of pollutants emitted by each vehicle, with its prescribed value. It also shows the Bharat stage norms each car is following, and their registration dates are in the chronological order.      Table 3 displays the value/level for vehicles using diesel as a fuel type. Emission from diesel vehicles is measured on the basis of HSU (Hartridge Smoke Unit), which is a unit of measurement used to measure the capacity of exhaust gases during emission. The HSU limit for pre-Bharat Stage 4 norms was 65, and for Bharat Stage 4 norms, it has been reduced to 50. Some of the major maker/companies being showcased through the table are Toyota, Maruti Suzuki, Hyundai, Honda, Mahindra, TATA and some luxury makers. As can be seen from the information mentioned above, we used vehicles from both indigenous and foreign makers/companies, thus adding another dimension to the analysis. The given data of HSU range from the value of 30.90.86 to 46.01.43, leading to the conclusion that most of the diesel vehicles are well below the current prescribed limits of HSU emission, yet the pollution levels are increasing at an alarming rate. Here we can also conclude that some of the old cars are well maintained and not emitting a large number of pollutants; it may be because the regular maintenance and service by car owner. Many old-car owners followed the pollution-under-control norms introduced by the Government of India. They always adopt new steps for reducing the pollution emission, while driving their cars. The following are the steps that can be helpful for someone for reducing the maintenance cost of vehicles, as well as the emission of pollution, too. Everyone needs to keep vehicles well-tuned and inflate the tires regularly, use biofuels such as CNG for regular derive, kept regular maintenance and test vehicles every 3 months by nearby installed pollution-under-control-norms center.
Details about the petrol type fuel are presented in Table 4, in which emissions are measured from three different pollutants which are CO (Carbon Monoxide), HC (Hydrocarbons) and CO 2 (Carbon Dioxide). Another parameter that is being measured for petrol driven vehicles is Lambda (λ), indicating the optimum conditioning needed for the proper functioning of catalytic converters. The vehicles registered during the pre-Bharat Stage 4 norms are only tested for CO and HC, having a prescribed limit of 0.5 and 750 ppm. For Bharat Stage 4 norms which were adopted in 2010 the prescribed limit for CO and HC are 0.3 and 200 ppm; Lambda should be in the range of 0.97 to 1.03. The given data of CO ranges from 0.001 to 0.380 ppm, and for HC, the data range from 0 to 197 ppm. The given data for both the pollutants have a large range, which shows that there are many parameters which give any vehicle its emission results, e.g., the distance traveled and the terrain on which the vehicle has been driven, the maintenance of the vehicle and the maker/company of the vehicle. Table 5 showcases the details about vehicles that operate/run on petrol/CNG. For such vehicles, only CO and HC are measured with the same prescribed limit as according to pre-BS4 and BS4 norms; Lambda (λ), as a parameter, is not measured for such vehicles. In the data collected for petrol/CNG, the value of CO ranges from 0.001 to 0.310 ppm, and the value of HC ranges from 0 to 187 ppm. We can also notice that the data for petrol and petrol/CNG driven vehicles almost have the same range.
Tables 6-8 displays the average emissions over different years of HSU for diesel-driven vehicles and CO, HC and CO 2 for petrol and for petrol/CNG-driven vehicles. Calculating the average emission over different years helps in realizing how a change in technology over the year can affect vehicular emissions. The average emissions in chronological order for vehicles operating from a diesel engine are given by Table 6   year. This is a matter of concern. New advancement in automobile industries do not take this into consideration to maintain these values.

Result Analysis
Our analysis is based on the data collected from the different pollution tracker nodes installed across the different locations in Delhi NCR. The analysis shows that few parameters need to be a concern for reducing the pollutants emission by vehicles. These major parameters are the high survival rates, decrease in annual mileage and major enforcement for three-to-five-year-old vehicles. In Table 2, we can track out that a large number of old vehicles are used in different regions after the various notifications in regard to banning old vehicles by the Government of India. These old vehicles are the major source of vehicle pollutants (Figures 2-4).
In Table 2, we can track out that a large number of old vehicles are used in different regions after the various notifications in regard to banning old vehicles by the Government of India. These old vehicles are the major source of vehicle pollutants (Figures 2-4).   In Table 2, we can track out that a large number of old vehicles are used in different regions after the various notifications in regard to banning old vehicles by the Government of India. These old vehicles are the major source of vehicle pollutants (Figures 2-4).   This situation can be handled by introducing the low survival rate for vehicles. It would correspond to easy replacement or breakdown of old vehicles. Thus, after introducing this, the pollutants share of old vehicles would be low. Lowering the survival rate will down the percentage of pollutants emission by old vehicles.
Lowering the mileage can also result in low fuel consumption and reduce emissions, too. The vehicles can be categorized in different mileage levels. For new vehicles, the mileage should be high, and for old vehicles, those having a high emission, the mileage level should be low. Major enforcement is also needed for reducing vehicle pollution. Time to time, vehicle services and enforcement are very important to reduce the pollutants emission by vehicles ( Figure 5). The current study can make significant correlations with the impact of emission components toward sustainable development. We can further investigate in terms of green ICT and pollution, as well. In the future, based on several available studies found from the work done by several researchers, we may try to further explore the solutions for reducing pollutants. We can find some IoT sensor-enabled technologies to raise alarms if the pollution level or emission of specific gases, such as CO, CO 2 and HC, go beyond the acceptable limits [63][64][65][66][67][68]. This situation can be handled by introducing the low survival rate for vehicles. It would correspond to easy replacement or breakdown of old vehicles. Thus, after introducing this, the pollutants share of old vehicles would be low. Lowering the survival rate will down the percentage of pollutants emission by old vehicles.
Lowering the mileage can also result in low fuel consumption and reduce emissions, too. The vehicles can be categorized in different mileage levels. For new vehicles, the mileage should be high, and for old vehicles, those having a high emission, the mileage level should be low. Major enforcement is also needed for reducing vehicle pollution. Time to time, vehicle services and enforcement are very important to reduce the pollutants emission by vehicles ( Figure 5). The current study can make significant correlations with the impact of emission components toward sustainable development. We can further investigate in terms of green ICT and pollution, as well. In the future, based on several available studies found from the work done by several researchers, we may try to further explore the solutions for reducing pollutants. We can find some IoT sensor-enabled technologies to raise alarms if the pollution level or emission of specific gases, such as CO, CO2 and HC, go beyond the acceptable limits [63][64][65][66][67][68].

Conclusions
This study presents the gaseous pollutants (181) emission factors of 181four-wheeler cars from different companies and of different types of fuels. The measurement of gaseous pollutants was done for Delhi, the most polluted city in India. Table 3 displays the value/level for vehicles using diesel as a fuel type. Emission from diesel vehicles is measured based on HSU (Hartridge Smoke Unit), which is a unit of measurement used to measure the capacity of exhaust gases during emission. Some of the major makers/companies being showcased through the table are Toyota, Maruti Suzuki, Hyundai, Honda, Mahindra, TATA and some luxury makers. The given data of HSU range from the value of 30.90.86 to 46.01.43, leading to the conclusion that most of the diesel vehicles are well below the currently prescribed limits of HSU emission, yet the pollution levels are increasing at an alarming rate. Here we can also conclude that some of the old cars are well maintained and not emitting a large number of pollutants; it may be because of the regular maintenance and service by the car owner. This study is also demonstrating the different HSU values emitted by the different companies' cars. The results also demonstrate that the new advancement in automobile industries is not very much concerned about maintaining the HSU level for vehicles.
Details about the petrol-type fuel show that the cars registered in 2015 emit higher amounts of pollutants as compared to those emitted by the cars registered in 2004. However, in the cars registered after 2015, the CO and HC values come down rapidly. On the other side, if we will look at the

Conclusions
This study presents the gaseous pollutants (181) emission factors of 181four-wheeler cars from different companies and of different types of fuels. The measurement of gaseous pollutants was done for Delhi, the most polluted city in India. Table 3 displays the value/level for vehicles using diesel as a fuel type. Emission from diesel vehicles is measured based on HSU (Hartridge Smoke Unit), which is a unit of measurement used to measure the capacity of exhaust gases during emission. Some of the major makers/companies being showcased through the table are Toyota, Maruti Suzuki, Hyundai, Honda, Mahindra, TATA and some luxury makers. The given data of HSU range from the value of 30.90.86 to 46.01.43, leading to the conclusion that most of the diesel vehicles are well below the currently prescribed limits of HSU emission, yet the pollution levels are increasing at an alarming rate. Here we can also conclude that some of the old cars are well maintained and not emitting a large number of pollutants; it may be because of the regular maintenance and service by the car owner. This study is also demonstrating the different HSU values emitted by the different companies' cars. The results also demonstrate that the new advancement in automobile industries is not very much concerned about maintaining the HSU level for vehicles.
Details about the petrol-type fuel show that the cars registered in 2015 emit higher amounts of pollutants as compared to those emitted by the cars registered in 2004. However, in the cars registered after 2015, the CO and HC values come down rapidly. On the other side, if we will look at the emission of CO 2 by the vehicles registered in 2010, 2015 and 2019, we see the same value of CO 2 emitted by the old and new cars. The results also demonstrate that the new advancement in automobile industries is not very much concerned about maintaining the CO 2 level for vehicles. The outcome for petrol/CNG cars indicates that few petrol/CNG cars are emitting a large number of pollutants. The cars registered in 2019 are emitting higher pollutants compared to the cars registered in 2005. This is due to the easy availability of unauthorized installation of CNG kits in the Delhi NCR region. Yes, to reduce the expenses on travel, everyone is now adopting the easy installation of CNT kits from an unauthorized dealer. No one cares about the effect of unauthorized installation on pollutant emission.
Overall, the analysis shows that few parameters need to be a concern for reducing the pollutants emission by vehicles. These major parameters are the high survival rates, decrease in annual mileage and major enforcement for three-to-five-year-old vehicles. The unauthorized installation of CNG kits also has to be banned strictly. Secondly, technological advancement not only targets fuel efficiency but also targets to reduce CO, CO 2 and HC. This study shows that many old vehicles are used in different regions after the various notifications regarding banning old vehicles by the Government of India. These old vehicles are the major source of vehicle pollutants. These old vehicles need to be banned immediately. This study will also help pollution-monitoring authorities make new and effective policies against the emission of pollutants by the vehicles. The significant contributions that were made by the work in this paper are summarized below:

1.
Presents the gaseous pollutants (Hydrocarbons (HC), Carbon Monoxides (CO) and Carbon Dioxide (CO 2 )) emission factor of 181 four-wheeler cars from different companies and of different type of fuels.

2.
Based on this statistical data obtained and analyzed, the scenarios regarding future vehicle growth rate and its impact on air quality are mentioned, to overcome emission problems. 3.
The analysis shows that few parameters need to be a concern for reducing the pollutants emission by vehicles. These major parameters are the high survival rates, decrease in annual mileage and major enforcement for three-to-five-year-old vehicles.

4.
This study shows that many old vehicles are used in different regions after the many notification regards to banning old vehicles by the Government of India. These old vehicles are the major source of vehicle pollutants.

5.
The unauthorized installation of CNG kits also has to be banned strictly. Secondly, technological advancement not only targets fuel efficiency but also targets the reduction of CO, CO 2 and HC. 6.
It will be helpful to pollution-monitoring authorities for making new and effective policies against the emission of pollutants by the vehicles. Funding: This research received no external funding.