Role of Motor Vehicle Lifetime Extension in Climate Change Policy

Jan 25, 2011 - Industrial Ecology Programme, Norwegian University of Science and Technology, Trondheim, Norway. ⊥ Department of Geography, Universit...
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Role of Motor Vehicle Lifetime Extension in Climate Change Policy Shigemi Kagawa,*,† Keisuke Nansai,‡ Yasushi Kondo,§,|| Klaus Hubacek,^ Sangwon Suh,# Jan Minx,r Yuki Kudoh,O Tomohiro Tasaki,‡ and Shinichiro Nakamura§ †

Faculty of Economics, Kyushu University, Fukuoka, Japan Research Center for Material Cycles and Waste Management, National Institute for Environmental Studies, Tsukuba, Japan § Faculty of Political Science and Economics, Waseda University, Tokyo, Japan Industrial Ecology Programme, Norwegian University of Science and Technology, Trondheim, Norway ^ Department of Geography, University of Maryland, Maryland, United States # Bren School of Environmental Science and Management, University of California, Santa Barbara, California, United States r Department for the Economics of Climate Change and Department for Sustainable Engineering, Technische Universit€at Berlin, Berlin, Germany O Research Institute of Science for Safety and Sustainability, National Institute of Advanced Industrial Science and Technology, Tsukuba, Japan

)

‡

bS Supporting Information ABSTRACT: Vehicle replacement schemes such as the “cash for clunkers” program in the U.S. and the “scrappage scheme” in the UK have featured prominently in the economic stimulation packages initiated by many governments to cope with the global economic crisis. While these schemes were designed as economic instruments to support the vehicle production industry, governments have also claimed that these programs have environmental benefits such as reducing CO2 emissions by bringing more fuel-efficient vehicles onto the roads. However, little evidence is available to support this claim as current energy and environmental accounting models are inadequate for comprehensively capturing the economic and environmental trade-offs associated with changes in product life and product use. We therefore developed a new dynamic model to quantify the carbon emissions due to changes in product life and consumer behavior related to product use. Based on a case study of Japanese vehicle use during the 1990-2000 period, we found that extending, not shortening, the lifetime of a vehicle helps to reduce life-cycle CO2 emissions throughout the supply chain. Empirical results also revealed that even if the fuel economy of less fuel-efficient ordinary passenger vehicles were improved to levels comparable with those of the best available technology, i.e. hybrid passenger cars currently being produced in Japan, total CO2 emissions would decrease by only 0.2%. On the other hand, we also find that extending the lifetime of a vehicle contributed to a moderate increase in emissions of health-relevant air pollutants (NOx, HC, and CO) during the use phase. From the results, this study concludes that the effects of global warming and air pollution can be somewhat moderated and that these problems can be addressed through specific policy instruments directed at increasing the market for hybrid cars as well as extending lifetime of automobiles, which is contrary to the current wisdom.

1. INTRODUCTION Vehicle replacement schemes have featured prominently in the economic stimulation packages of many governments as a means of overcoming the global economic crisis. Overall, the governments of at least 13 countries, including the world’s largest vehicle producing nations,1-3 have introduced vehicle replacement schemes. Japan has also introduced a similar vehicle replacement scheme from April 10, 2009 to September 30, 2010 (see S7 of the SI). These schemes are generally considered to have successfully encouraged vehicle owners to replace their cars. For example, the German scheme was introduced in February 2009, and, to date, 1.2 million motorists - twice the expected number - have applied to take part in the program.4 In the U.S., $2.8 billion was approved for the Car Allowance Rebate System (CARS), commonly referred to as the “cash for clunkers” program, exceeding the government’s initial $1 billion allocation.5 r 2011 American Chemical Society

Apart from economic justifications (e.g., avoidance of a liquidity trap), participating governments have also claimed that their vehicle replacement schemes benefit the environment. For instance, when announcing the CARS program, U.S. Transportation Secretary Ray LaHood noted, “This is good news for our economy, the environment and consumers’ pocketbooks.”.6 It is often argued that these schemes will help curb the increase in CO2 emissions and other air pollution from the transportation sector by replacing less fuel-efficient vehicles with more fuel efficient ones. However, little evidence is available to support this claim as the few existing studies (e.g., ref 7) have failed to Received: October 13, 2010 Accepted: January 3, 2011 Revised: December 20, 2010 Published: January 25, 2011 1184

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Environmental Science & Technology systematically consider the trade-offs between fuel efficiency improvement and additional vehicle fleet production due to the replacement. A recent empirical contribution about this problem by Mazzi and Dowlatabadi8 estimated the impacts of growing the stock of diesels on health-relevant air pollutants and provided a comprehensive evaluation on environmental effects between 2001 and 2020 in UK. Mazzi and Dowlatabadi (2007) did not treat the vehicle lifetime in their forecasting framework, which is explicitly included in our study. This paper focuses on the gasoline vehicle replacement schemes of Japan, and we statistically estimate the vehicle lifetime distributions addressing the effect of decreasing the life of passenger cars on the mitigation of global warming and the improvement of air quality. It should be noted that car ownership of diesel passenger vehicles amounted to only about 8% of total passenger vehicles in 2000 in Japan and that gasoline passenger vehicles have been more popular than diesel passenger vehicles since 1978.9

2. VEHICLE LIFETIME AND ITS IMPACT ON THE ECONOMY AND THE ENVIRONMENT Increasing the number of years that motor vehicles are used generally reduces the number of new motor vehicles that will be sold. Therefore, an extension of motor vehicle lifetime would have an adverse effect on the sales of the car industry and the contribution of the vehicle industry to GDP of the producing country. However, the lower levels of energy consumption associated with decreased vehicle production would benefit the environment. In addition, the increased lifetime of cars would negatively affect the fuel efficiency of the average vehicle in a country’s fleet, as older and thus generally less fuel-efficient vehicles would be in use for a longer period of time, which would have negative environmental implications. Similarly, policies directed toward extending vehicle lifetime would be subject to two types of what are referred to as rebound effects. The first such effect is that a longer vehicle life would reduce consumer spending on new vehicles, resulting in consumers spending their additional disposable income on other goods and services and generating additional carbon emissions in the sectors that produce them. Conversely, a shorter lifetime would have the opposite results. The second rebound effect might arise if consumers buy more fuel-efficient vehicles and the energy cost per unit distance decreases due to improved fuel economy, vehicle owners may be inclined to drive farther, which may increase overall energy consumption.10 In both cases, one of the primary concerns of energy economists are how to measure these rebound effects and also how large they are in the shortterm and long-term.11-15 These rebound effects are directly influenced by changes in motor vehicle lifetime (i.e., product durability) and by energy costs per unit distance. A recent empirical contribution also shows that the fuel economy itself has been affected by the “Cash For Clunkers” program which increased the average fuel economy of purchased new light-duty vehicles by about 0.6-0.7 miles per gallon during the period: July-August, 2009 in U.S.16 Consequently, the improved fuel economy through the “Cash For Clunkers” program will further lead to an increase in driving distance. Another important question is how the “Cash For Clunkers” program affected the implied carbon cost of CO2 reductions. For this question, Knittel (2009) estimated that the implied cost of CO2 is $516, $365, and $269 for three, four, and five year scrappage time and found that these estimates are remarkably affected by the variation of the

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rebound elasticity.17 Knittel (2009) also attempts to estimate the cobenefits from reducing health-relevant air pollution as in ref 8. An important and as yet seemingly unaddressed question is how do the changes in motor vehicle lifetimes affect the sales of new motor vehicles and gasoline through the physical stock-flow relationship of motor vehicles, and how does the production and use of these motor vehicles subsequently affect life-cycle CO2 emissions and health-relevant air pollution.18 To the best of our knowledge, this study is the first attempt to empirically investigate the impacts of the lifetime shifts of a vehicle on the life-cycle CO2 emissions and other air pollution throughout the supply chain and argue the trade-off relationship between car lifetime and desirable fuel efficiency level from the point of view of the life-cycle CO2 emissions.

3. METHODS AND DATA In previous studies,25,26 we have incorporated product lifetime distribution into a static energy accounting model19-24 and developed a dynamic energy accounting model with specified product lifetime distributions. In this paper, this framework is modified to analyze the effects of shortening of lifetime of less fuel-efficient ordinary passenger cars on CO2 emissions induced by motor vehicle manufacturing, CO2 emissions due to motor vehicle use (i.e., fuel combustion), and CO2 emissions generated throughout the supply chain (see refs 27 and 28 for the seminal LCA studies). We further estimated the magnitude of fuel efficiency improvements in passenger cars that will be required to offset the increase in emissions associated with the production of new motor vehicles in response to reduced motor vehicle lifetimes (e.g., refs 29 -31). 3.1. Product Lifetime Distribution Model. In some previous studies, the number of vehicles disposed of over time was modeled so as to depend upon economic factors such as repair costs, the price of purchasing a new car, the price of gasoline and the unemployment rate, and the validity of that models were then examined statistically.32 Other studies were primarily concerned with quantitatively analyzing the degree to which the vehicle disposal rate was influenced by either technical factors, such as physical wear and tear, or by economic factors, such as the cost of service and repair, vehicle prices, gasoline prices, and the unemployment rate (e.g., ref 33). If we assume that the technical and economic factors are independent of each other, then we can analyze what impact the vehicle disposal rate has on only the economic factors associated with the introduction of a vehicle replacement scheme. However, we believe it becomes increasingly difficult to completely separate out the impact of the disposal rate as time passes after the purchase of a new vehicle. As a consequence, as in previous studies,34-37 we have assumed that the disposal rate follows a certain lifetime distribution and have designed our analytical framework in which we estimate probability distributions of vehicle lifetime unconditional on those technical and economic factors. More specifically, we assumed that vehicle lifetime follows a generalized gamma distribution which is frequently used in the field of reliability engineering38,39 and estimated its parameters by the maximum likelihood method. The passenger cars are classified into three types: ordinary passenger car which has a larger internal-combustion engine than 660 cc, Kei passenger car which has an engine of 660 cc or smaller, and hybrid passenger car (see S7 for more information about the fleet). In line with the seminal contributions by 1185

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Cohen et al.,38,39 we assume that the product lifetime of a passenger car of type k follows a generalized gamma distribution. The probability density function (pdf) and cumulative distribution function (cdf) of the generalized gamma distribution, G(Rk,βk,Fk), are (   ) βk yFk βk - 1 y βk fG ðy; Rk , Fk , βk Þ ¼ exp ðy > 0Þ ð1Þ Rk ðRk ÞFk βk ΓðFk Þ and

  βk ! y , Fk ðy > 0Þ FG ðy; Rk , Fk , βk Þ ¼ P Rk

ð2Þ

respectively, where fG(y;Rk,βk) is the fraction of vehicles scrapped at lifetime y, FG(y;Rk,βk) is the cumulative fraction of vehicles scrapped by lifetime y, Rk is a scale parameter, βk is a shape parameter expressing the width of the lifetime distribution, Fk is another shape parameter, Γ represents the gamma function, and P represents the incomplete gamma function as follows Z ¥ Z z 1 Pðz, aÞ ¼ e - t t a - 1 dt with ΓðaÞ ¼ e - t t a - 1 dt ð3Þ ΓðaÞ

0

0

The average life of the generalized gamma distribution can be formulated as μk = Rk(Γ(Fkþ1/βk))/(Γ(Fk)) (see p 221 of ref 38). Interestingly, the Weibull distribution function is a special case of the generalized gamma distribution function, in which Fk = 1. As in Kagawa et al.,25,26 we developed a dynamic CO2 emission model using the lifetime distributions (see S1). The limitations of the proposed model are also presented in S2. 3.2. Data and Scenario Analysis. Table S4 shows the results of estimated lifetime distributions of ordinary motor vehicles. The estimated average lifetimes are fairly stable during six years, while the estimates of parameters are not; we interpreted the results as support for our procedure in which we did not assume the stability of lifetime distributions over time but allowed them to be different. As shown in Tables S4 and S5, we found that there are clear differences in the estimated average lifetimes between the Weibull and generalized gamma distributions, and the likelihood ratio tests rejected the hypothesis that vehicle lifetimes follow a Weibull distribution, i.e., Fk = 1, at the 1% significance level for all the cases considered. Using the generalized gamma distribution model with the scale and shape parameters presented in Table S4, we performed a scenario analysis by changing the average lifetime of less fuelefficient ordinary passenger cars. More specifically, the average lifetime of a generalized gamma distribution G(Rk,βk,Fk) is given by μk = Rk(Γ(Fkþ1/βk))/(Γ(Fk)), which is proportional to the scale parameter Rk. The baseline lifetime distribution is a generalized gamma distribution with the parameter estimates, ^ ,F ^k, β GðR k ^k Þ. By manipulating the scale parameter, we were ^ ,F able to formulate a lifetime distribution, say GðR0 , β k ^k Þ, for 0 which the scale parameter R was chosen so as to equate μ0 ¼ ^ Þ Γð^ F þ 1=β

R0 kΓð^F Þ k and a given level of average lifetime in scenario k analyses below. Figure S1 shows changes in the cdf of the lifetime distributions when the average lifetime of ordinary passenger cars newly registered each year are moved in one-year increments from -3 years to þ3 years. The same procedure could not be applied to the Kei and hybrid passenger cars due to the lack of reliable data. As for the cars of these types, therefore, we employed the observed numbers of cars in use for all the cases in scenario analyses below.

Given a change in the average lifetime of ordinary passenger cars that were newly purchased from 1990 to 2000, we could calculate the number of cars disposed of in each year, Dt1 in eq S2, following formulated lifetime distributions. We could also calculate the number of new cars sold in each year because the total number of cars owned in a given year in our model would remain constant, even if there was a change in the lifetime of a passenger car. However, a change in the lifespan of an ordinary passenger vehicle would affect the sales of new Kei and hybrid passenger cars. We were unable to statistically estimate their lifetime distributions, as mentioned above. Therefore, the numbers of Kei and hybrid cars that were influenced by the change in the life of ordinary passenger cars were assumed not to have been disposed, and they remained in use during the study period. In addition to the number of each type of motor vehicle in use, a given change in the average lifetime of ordinary passenger cars would influence the total distance traveled and demand for gasoline consumption because they depend upon the average distance traveled per year per vehicle for each vehicle type as well as the average fuel efficiency (Table S1). For instance, if the average lifetime of ordinary vehicles is shortened, the percentage of the Kei passenger cars to all the cars in use would increase, which leads to an improvement of average fuel efficiency, and the total distance traveled would decrease. The changes are consistent with the trend in the real world, and we account explicitly of the effect (see S2). Subsequently, we estimated the life-cycle CO2 emissions induced by motor vehicle production, gasoline refinery (gasoline production), and associated wholesale, retail, and transport services using the competitive imports type input-output model 25,26 (see S1 for details). The direct CO2 emission originating from gasoline combustion were estimated, as well. Table S2 in SI shows the emission intensities estimated in this study. The data sources used in this study are summarized in S8.

4. RESULTS 4.1. Effects of Changes in Motor Vehicle Lifetime on CO2 Emissions. We examined the vehicle replacement behavior of

ordinary passenger car users (>661 cc), which are less fuelefficient than other types of cars. To do this, we analyzed the changes in the associated CO2 emissions for cases of prolonged and curtailed use in ordinary passenger cars newly registered between 1990 and 2000. Consider the scenario of a one-year increase in average car lifetime of ordinary passenger cars during the study period (1990-2000). Under such a lifetime-extension scenario, the average lifetime of an ordinary passenger car newly purchased in 1990 increases from the baseline lifetime of 11.36 years to 12.36 years (Figure S1). The opposite scenario (i.e., a scenario in which there is a one-year decrease in average lifetime) is also investigated. In the 1990-2000 period, the effects of changes in the average lifetime of vehicles on CO2 emissions due to vehicle purchases (the first term of eq S7 in the SI), the CO2 emissions due to gasoline purchases (the second term of eq S7), and the direct CO2 emissions associated with gasoline combustion by vehicles on the road (the third term of eq S7) can be estimated using the dynamic CO2 emission model (Section 2 and S1). Figure 1 shows the results of our estimation. The horizontal axis of Figure 1 shows the extension and reduction in the average life of a vehicle over the study period. The vertical axis shows the result of subtracting the amount of CO2 emissions due to a 1186

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Figure 1. Effects of changes in the average lifespan of ordinary passenger cars newly registered between 1990-2000 on CO2 emissions in 2000.

change in lifetime from the 73 million tons of CO2 emissions produced in 2000 (baseline data) when no lifetime extension or reduction occurs. Thus, a positive value on the vertical axis indicates that a change in lifetime leads to an increase in CO2 emissions, with a negative value indicating a decrease in CO2 emissions. The results in Figure 1 imply that the CO2 emissions associated with motor vehicle manufacturing substantially decrease as car lifetime is extended, even though gasoline combustion-derived CO2 emissions increase. The reason for this is that an extension in motor vehicle lifetime has the effect of reducing the number of new motor vehicles sold, thereby reducing the number of motor vehicles produced and the amount of CO2 emissions attributable to motor vehicle manufacturing. However, this extension in car lifetime results in an increase in the number of old and less fuel-efficient vehicles still in service, increasing the CO2 emissions from the vehicle fleet still on the road. A critical consideration here is that total induced CO2 emissions, i.e. the combined emissions from motor vehicle production, gasoline refining, gasoline combustion, and other services (see “Total” in Figure 1), decrease in response to an extension in motor vehicle lifetime. This finding implies that the product lifetime extension scenario would clearly contribute to a reduction in carbon emissions. In addition, Figure 1 also suggests that shorter motor vehicle lifetimes encourage an increase in the total amount of induced CO2 emissions. This is because a shorter motor vehicle lifetime would result in an accelerated car replacement cycle, which would lead to more new and fuel efficient motor vehicles on the road, which would in turn reduce gasoline combustionderived CO2 emissions. However, the reductions achieved in this manner are rendered less significant when considered against the relative contribution of the CO2 emissions associated with the production of new motor vehicles. The net result would be an increase in total CO2 emissions. 4.2. Fuel Efficiency Levels Required To Offset the Increased Emissions Associated with Shortening Motor Vehicle Lifetime. To completely offset the increase in emissions due

to a one-year reduction of average motor vehicle lifetime and maintain the same 73 million tons of emissions for the year 2000, the fuel efficiency of vehicles in 2000 must be improved by reducing emissions during the driving phase. Setting the 73 million tons of CO2 emissions as a constant, we can obtain fuel efficiency and the number of new vehicles to be produced, given a change in average vehicle fleet lifetime, base on the same model used for the scenario analysis above. The results formed the reciprocal emissions trajectory shown in Figure 2. The emission isoquant in Figure 2A shows that, to completely offset the emissions increase attributable to a one-year reduction in motor vehicle lifetime, an improvement in the fuel efficiency of approximately 12.7% would be required, i.e. from 12.1 km 3 L-1 to 13.6 km 3 L-1. If the fuel efficiency cannot be improved to more than 13.6 km 3 l-1, the relationship between the lifetime change and the fuel efficiency is in the increased-CO2 zone (see Figure 2A) and consequently the one-year reduction leads to the deterioration of the environment. Similarly, to reduce the lifetime of a vehicle by 3 years requires achieving an increase in fuel efficiency of approximately 17 km 3 per liter gasoline (i.e., 40 miles per gallon). The emissions isoquant shown in Figure 2B represents an increase of 236 billion yen in the demand for new cars generated by a one-year reduction in the lifetime of ordinary passenger cars. If the value of the demand for ordinary passenger cars in 2000 was 2847 billion yen, then a one-year reduction in vehicle lifetime would increase the demand by approximately 8.3%. Under this scenario, the activities of vehicle manufacturers would have an adverse effect on the environment unless they were able to achieve a fuel-efficiency improvement equivalent to approximately 1.5 times the rate of the increase in demand. Since the annual average rate of improvement in the fuel economy of ordinary passenger cars for the ten-year period between 1990 and 2000 was approximately 0.7%, achieving an increase of 1.5 times would be very difficult. 4.3. Levels of Hybrid Car Market Share Required To Offset the Higher Emissions Associated with a Decrease in Motor Vehicle Lifetime. Although shortening the average lifetime of 1187

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Figure 2. Relation (A) between the reduction in the average number of years during which ordinary passenger cars were used during 1990-2000 and the fuel efficiency of ordinary passenger cars necessary to offset the increased emissions associated with the reduction in years of use. Also shown is the relation (B) between the increase in demand obtained by a reduction in the average number of years of car use and the fuel efficiency of ordinary passenger cars that would be required to offset the increased emissions associated with the reduced duration of use.

relatively fuel inefficient ordinary passenger vehicles would increase sales in the vehicle industry, the volume of CO2 emissions produced would show a gradual upward trend. One measure to reduce the CO2 emissions would be to improve the fuel efficiency of newly purchased ordinary passenger cars. Another potential measure would be to have consumers aggressively purchase hybrid vehicles, the most fuel efficient of the three vehicle types, after disposing of their old cars. Although in 2000 the market share of hybrid vehicles was only 0.3% (and 14.1% in 2009), the expansion of this market share will lead to a reduction in the volume of emissions attributable to the driving phase. In this study, we estimated the rate of hybrid car market share expansion in 2000 that would be required to offset the increase in emissions influenced by the decrease in the average lifetimes of ordinary passenger vehicles that were newly registered between 1990 and 2000. We assumed that the market share of ordinary passenger cars would shrink in proportion to the amount that the market share of hybrid cars would expand. The results are presented in Figure 3, which shows that the 0.3% market share of hybrid cars would have to increase significantly, to 7.3%, in order to completely offset the higher levels of emissions discharged due to a one-year decrease in the average lifetime of fuelinefficient ordinary passenger cars. An important point is that even if the market share of the hybrid cars increased to 7.3%, it would conversely harm the environment in case of decreasing the lifetime larger than one year, because the CO2 increase associated with car production exceeds the CO2 decrease associated with car driving. Considering the present situation such that the market share of hybrid cars remarkably increased from 0.3% in 2000 to 14.1% in 2009 far higher than the offset level, 7.3%, our scenario analysis revealed that if the 2000 market shares of hybrid cars and ordinary passenger cars were 14.1% and 55.8%, respectively under the one-year decrease scenario during the study period, life-cycle CO2 emission in 2000 can be reduced by 0.6% and more than 2.1 years lifetime reduction conversely increases the CO2 emission under the 14.1% market share of hybrid cars. 4.4. Effects of Changes in Motor Vehicle Lifetime on Health-Relevant Air Pollution. In section 3.3, we analyzed the impact on life-cycle CO2 emissions due to shortening and

Figure 3. Relation between the reduction in the average number of years during which ordinary passenger cars were used during 1990-2000 and the market share of hybrid cars necessary to offset the increased emissions associated with the reduction in years of use.

extending the lifetime of an automobile. We quantitatively demonstrated that extending the lifetime of an automobile results in a reduction in life-cycle CO2 emissions and curbs global warming. One important problem is that although extending the lifetime of an automobile will decrease the contribution of vehicle emissions on global warming, the number of older automobiles that were purchased and newly registered during the period of relatively lax automobile emission regulations also increases, which means that there is actually a danger of air pollutants increasing.8 Consequently, this study focused also on other air pollutants emitted by automobiles (NOx, HC, and CO) and analyzed how either extending or shortening automobile lifetime affects the amounts of air pollutants emitted. We first calculated the total distance driven annually by each year and vehicle type by multiplying the average number of miles dtk in year t by the number of automobiles owned in year t, Ktkt-y (see S1). The number of automobiles owned during the ten-year period from 1990 to 2000 was estimated by changing the average 1188

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Environmental Science & Technology lifetime of an ordinary passenger car newly registered in the tenyear period from 1990 to 2000 (see Figure S1). It is important to note that the number of automobiles owned and newly registered before 1990 is assumed to have remained constant. Next, by multiplying the emissions factors (g/km) of the air pollutants (NOx, HC, and CO) for the vintages and vehicle types, as shown in Table S3, by the estimated annual distance driven by the vintage and vehicle type, we were able to determine the volume of emissions by vintage and vehicle type. We then estimated the air pollutant levels associated with changes in automobile lifetime by totaling the amounts of the air pollutant emitted by driving vintage vehicles and newly registered vehicles. By estimating air pollutant emissions in 2000 by assuming that there was no change in the average lifetime of an automobile, we see that about 43,300 tons of NOx, about 18,900 tons of HC, and about 459,500 tons of CO pollutants were emitted into the atmosphere. This study also finds the fluctuations in air pollutant volumes for the year 2000 due to changes in the lifetime of automobiles registered in 1990 and after (see Figure S4). These findings show that the quantity of air pollutants increases as the lifetime of automobiles is extended, and the reason for this was stated previously i.e. automobiles that were newly registered when emission regulations were lax continue to be driven due to extended automobile lifetimes. More specifically, a one year extension in automobile lifetime will result in an additional discharge of 285 tons of NOx, 119 tons of HC, and 2451 tons of CO into the atmosphere. The rates of increase in these air pollutants due to the extension in car lifetime are 0.66%, 0.63%, and 0.53%, respectively. Total emissions of NOx, non-methane volatile organic compounds (NMVOC), and CO in Japan in 2000 in Japan were 1959 (Kt), 1880 (Kt), and 2661 (Kt), respectively.46 A one-year extension in automobile lifetime contributed to an increase in the total volume of discharged emissions of 0.01%, 0.006%, and 0.09%, respectively. On the other hand, since a one-year extension in vehicle lifetime was equivalent to a 417 (Kt•CO2) reduction in CO2 emissions, the overall contribution of a one-year extension (see Figure 1) to total CO2 emissions in 2000 (1255 Mt•CO2) was -0.03%. Within the context of total emissions, the effect of automobile lifetime extension on the emission of NOx and HC from automobiles is limited. However, in cases where a change in lifetime has an impact on the volume of CO and CO2 emissions, then it becomes important to recognize the trade-off. However, according to the Ministry of the Environment, the average annual concentration of CO along roads was very low in 2000 (0.8 ppm). Indeed, none of the measurements exceeded environmental standards: the average value over an eight-hour period (