2015-18
Estimation of Social Costs of Highways in Japan
Fumitoshi Mizutani
Yusuke Suzuki
Shuji Uranishi

Estimation of Social Costs of Highways in Japan

Fumitoshi Mizutani* (Kobe University)
Yusuke Suzuki** (Kyushu Sangyo University)
Shuji Uranishi*** (Osaka City University)[Abstract]: This study estimates and evaluates the social costs of highways in Japan.

Five kinds ofsocial costs of vehicular transport are considered: traffic accidents, air pollution, noise, global
warming, and traffic congestion.

Major findings of this study are as follows.

increase at an accelerated rate as traffic volume increases.

First, social costs

Second, the largest component ofvehicular transport’s social costs on highways is traffic congestion, accounting for about 64%.
second largest component is traffic accidents, accounting for 24%.

The

Third, among vehicle types, thesocial costs of buses are largest, at 105 yen per vehicle-km, about 16 times higher than the social
costs of regular cars.

Last, total social costs for whole highway networks are about 678,212 million

yen, or about 0.13% of Japan’s GDP.

Compared with highway fare revenues and the operating

costs of highways, social costs equal 62.6% and 98.6%, respectively.
[Key words]: Social costs; Car transportation; Highway; External costs[JEL classification]: H4, H5, L9, Q5, R4

1. Introduction
The main purpose of this paper is to estimate and evaluate the social costs of highways inJapan.

In general, with more people concerned about protecting the environment at both local andglobal levels, dependence on vehicular transportation in cities has brought about problems.
much dependence on autos causes air pollution, which has detrimental health effects.
congestion wastes time, money, and energy.

Too

Traffic

The most troubling issue related to continuing*

Correspondence author: Graduate School of Business Administration, Kobe University, 2-1 Rokkodai,
Nada-ku, Kobe 657-8501, Japan. E-mail: toshi@kobe-u.ac.jp**
Faculty of Commerce, Kyushu Sangyo University, 2-3-1 Matsukadai, Higashi-ku, Fukuoka, 813-8503,
Japan. E-mail: Suzuki.y@ip.kyusan-u.ac.jp***
Graduate School of Economics, Osaka City University, 3-3-138 Sugimoto, Sumiyoshi-ku, Osaka
558-8585, Japan. E-mail: uranishi@econ.osaka-cu.ac.jp

1dependence on car use, however, is global warming.

In order to implement transport policies

conducive to creating a sustainable environment, it is necessary to measure correctly the social costsof vehicular transport such as traffic accidents, air pollution, noise, global warming, and traffic
congestion.

By using a data set from Japan, this paper aims to estimate the social costs of vehiculartransport on highways and to evaluate how extensive these social costs are by comparing, forexample, highway fares relative to GDP.
Our study has several distinguishing characteristics.

The most important point is that

we estimate each individual highway’s social costs by considering average speed at the peak period,
total traffic volume, types of vehicular transport, and so on.

Second, this study distinguishes fivekinds of social costs of vehicular transport for individual highways in Japan: 1) traffic accidents, 2)
air pollution, 3) noise, 4) global warming, and 5) traffic congestion.

Third, by using a data set ofover 50 individual highways in Japan in 2005, we analyze the relationship between the social costsof vehicular transport and traffic volumes in general.

Last, by comparing highway fares, the degreeof GDP, the fuel tax level, and other factors, we assess the magnitude of social costs, for the purposeof creating prudent transport policy.
In order to attain the objectives mentioned above, we organize our study as follows.
we explain our method for estimating social costs.

First,In this section, we describe specific equations

for the five main categories of highways’ social costs.

The main methodology follows Mizutani etal. (2011), the main difference being that this study concerns highways while Mizutani et al. (2011)
focuses on traffic in cities.

Second, based on these equations, by using a data set for highways inJapan, we estimate the social costs of vehicular transport on highways.

Last, by comparing

highway fares, GDP and so on, we evaluate how extensive highways’ social costs actually are.

In

this section, we also summarize our major findings.

2. Previous Literature
In this section, we survey previous studies on the social costs of intercity car transportationsuch as Levinson and Gillen (1998), Levinson et al. (1999), Forkenbrock (1999), Ozbay, Bartin andBerechman (2001), Ozbay, Bartin, Yanmaz-Tuzel and Berechman (2007), Van Essen et al. (2004)
and Perez-Martinez and Vassallo-Magro (2013).
Levinson and Gillen (1998) develop a full cost model of a highway system, comprised ofuser, infrastructure, and time costs, as well as the social costs incurred by accidents, noise and air
pollution.

In this study, infrastructure costs are estimated by the regression method (OLS).
Levinson et al. (1999) investigate the full cost of transportation in order to comparetransportation modes. They compare three intercity transportation modes such as airplane, highway
and high-speed trains relative to the situation in the California corridor between Los Angeles and2

San Francisco. As there is to date no high-speed train in California, the French TGV is usedhypothetically for the estimation. Social costs estimated in this study are (i) traffic accidents, (ii)traffic congestion, (iii) noise, and (iv) air pollution.

As a result, total social costs were 0.0073 for

air transportation, 0.0020 for high-speed train and 0.0122 US dollar per passenger kilometer.

Asfor highway, social cost is about 5.3% of full cost.
Forkenbrock (1999) estimates both private cost and external cost (i.e. social cost) inintercity freight transportation in the US in 1994.

External costs in this study include (i) traffic

accidents, (ii) air pollution, (iii) the greenhouse effect, (iv) noise and (v) other external costs.

These

external costs are 1.11 US dollars per ton-mile in 1994, accounting for 11.6% of full costs.
By using a New Jersey data set, Ozbay, Bartin and Berechman (2001) also estimate thefull marginal costs of highways, comprised of vehicle operating, congestion, accident, environmental
and infrastructure costs.
In a further study, Ozbay, Bartin, Yanmaz-Tuzel and Berechman (2007) estimate the fullmarginal costs of highways for New Jersey’s highway network.

This cost is estimated based on

marginal cost function for specific OD (i.e. origin and destination).

Social costs in this study

consist of (i) congestion, (ii) traffic accidents, (iii) air pollution and (iv) noise.

Social costs are 6.57

US dollars per trip and account for 37.9% of full highway costs.
In a study by Van Essen et al. (2004) on the marginal costs of infrastructure use, theauthors examine the three transportation modes of road, railway and air transportation.
included in this study are infrastructure, traffic accidents, air pollution and noise.

Costs

As an example ofintercity road truck transportation, the marginal costs of road use in the Hamburg-Munich corridor(about 720km) in Germany in 2001 are estimated.

Social marginal costs in this case are 0.18 Euros

per vehicle and account for 75% of full marginal costs.
Perez-Martinez and Vassallo-Magro (2013) analyze the decreasing trend in the externalcosts of freight transportation in Spain.

In this study, the items included in external costs are traffic

accidents, air pollution and climate change for both trucks and railways. The authors estimate thatthe external costs of trucks are 2.35 Euros in 2005, and that the costs of trucks are 8 times higher
than those of railways.
Although there have been many studies on social costs, issues remain to be resolved. First,
there is much variation in the degree of social costs, indicating that costs might be affected by regionand situation.

Second, the items included in social costs (i.e. congestion, air pollution, noise, traffic

accidents and global warming) are not estimated together.

Third—and this is related to the second

reason—it is not clear what type is greatest among social costs. Furthermore, there is inadequate
analysis of the relationship between kinds of vehicle and the degree of social costs.1

1

In conclusion,

Some studies such as Koyama (2004), Van Essen et al. (2004) and Nishikawa and Kon (2011)3

there still much room for work in the investigation and analysis of the social costs of highways.

3. Methods for Estimation of Social Costs
3.1 Definition of Social Costs
The general models for the estimation of social costs of vehicle transport follow Mizutani
et al. (2011).

Although Mizutani et al. (2011) estimate social costs for each individual city, thisstudy estimates costs for each individual highway.

The social costs of vehicular transport consistof five items: traffic accidents, air pollution, noise, global warming, and traffic congestion.
Therefore, the social costs of vehicle transport are defined as equation-(1).

SCa = Cacc,a + Cair,a + CdB,a + Cwar,a + Ccon,awhere,(1)

SCa：Social costs of vehicular transport for highway-a,Cacc , a ：Social costs of traffic accidents for highway-a,
Cair , a ：Social costs of air pollution for highway-a,

C dB , a ：Social costs of noise for highway-a,
Cwar , a ：Social costs of global warming for highway-a,
C con , a ：Social costs of traffic congestion for city-a.
3.2 Traffic Volumeb

The traffic volume of vehicle type-b on section-c of highway-a ( Qa ) is estimated as
equation-(2) shows.

Thus, the basic formula for the estimation of traffic volume is obtained fromresults of daily traffic volume on the observed road section.

Observed daily traffic volume is€ carried out mainly on bigger
shown in the 2005 Road Transport Census, with observation being
roads and trunk roads.

⎡
⎤
⎡
⎤
Qab = d ⋅ ⎢∑ DISa ,c ⋅ CARab,c ,w , ⎥ + (365 − d ) ⋅ ⎢∑ (DISa ,c ⋅ CARab,c ,h )⎥
⎣ c
⎦
⎣ c
⎦ ,

(

where

€

)

(2)

Qab：Annual traffic volume of vehicle type – b on highway-a (vehicle-km),
DIS a ,c ：Length of observed section-c on highway-a (km),b：Daily traffic volume of vehicle type-b on section-c of highway-a for day type-k
CARa,c,k(vehicle/day),€distinguish vehicle types, but these studies consider only noise.

4d : number of weekdays (d=246 days),
a: highway , b: type of vehicle (1= car, 2 = bus, 3 = small truck, 4 = truck), c: section of
highway, k: day type (w = weekday, h = weekends).
3.3 Peak Period
In this study, we distinguish peak-time period and off-peak-time period.

We set up two

peak-time periods totaling 6 hours, consisting of 3 hours in the morning and 3 hours in the evening.
For each peak-time and off-peak-time period, we set up the speed of vehicle and traffic volume
individually.
However, when we observe the real data for highways, there are highways withconsiderable traffic volume even in off-peak-time periods, especially in rural areas, where webelieve that in fact there is no peak-time period.

We did not set up peak-time and off-peak-time

periods for 5 sections of highways because the estimated traffic volume exceeds the real numbers.
3.4 Speed on Highways
As for speed on highways, we estimate speed by distinguishing weekday or weekend,
peak-time or off-peak-time.

However, if the estimated speed on the section of a highway is higher

than the designated speed limit of the section of the highway, we set the designated speed limit as
the speed for that section.
There are two estimation methods of speed on highways.

For the first, we use existingdata on speed on a section of highway, if such data are available.

As vehicle speed at the peak

period, we use the existing data on vehicle speed.

However, as data on vehicle speed during theoff-peak period does not exist, we estimate the vehicle speed of a section of highway by using therelationship between speed and traffic volume at the peak-time period.

Based on the data on

vehicle speed and traffic volume at the peak-time period by type of highway, we obtain the results
shown in Table-1.
Table-1 Estimated Vehicle Speed-Traffic Volume Relationship on Highways
Type of highway
Highway with a speed limitof 100km/h
Highway with a speed limitof 80kmHighway with a speed limitof less than 80km

Estimated Speed-Traffic Volume Equations
2
Va = − 0.000019 q a2,line + 0.018 q a ,line + 82.58 adjR = 0.253 N = 358( −0 , 00000284 )( 0.0043 )(1.40 )

2
Va = − 0.000022 q a2,line + 0.021 q a ,line + 76.34 	
  adjR = 0.195 N = 406( −0 , 0000036 )( 0.00557 )(1.65)

2

Va = − 0.0069 q a,line + 78.81	
  	
  	
  	
  	
  	
  	
  	
  adjR = 0.049( 0.0020)(1.10)

5

N = 209

Urban Highway with aspeed limit of 80km
Urban Highway with aspeed limit of less thanVa = − 0.000072 q a2,line + 0.080 q a ,line + 58.31( −0 , 00000716 )( 0.0344 )Va = − 0.016 q a ,line + 57.56( 0.0137)( 6.366)(13.23)	 adjR2 = 0.580 N = 27

	
  	
  	
  	
  	
  	
  adjR 2 = 0.203 N = 96

80km

(Note): Va ：Vehicle speed (km/h) per lane on highway – a,qa,line ：Traffic volume (vehicle/h) per lane€
4. Models for the Estimation of Individual Social Costs
In this section, we will summarize the models for estimating five kinds of social costs ofvehicular transport on a highway: (i) traffic accidents, (ii) air pollution, (iii) noise, (iv) global
warming, and (v) traffic congestion.

The basic models summarized here are based on Mizutani etal. (2011).
4.1 Traffic Accidents
First, the social costs of traffic accidents are estimated by multiplying the unit social costof traffic accidents by the number of victims resulting from traffic accidents, as equation-(3) shows.
As these social costs vary according to type of damage, we distinguish types of victims.

(3)

Cacc,a = ∑(Pacc,e ⋅ POPacc,a,e )ewhere,

Cacc,a：Social costs of traffic accidents on highway – a (yen),Pacc,e：Unit social cost of traffic accident type – e (yen),€

POPacc,a,e：Number of victims of type- e caused by traffic accidents (persons),
e：Type of victims (1: death, 2 : injured)2
Based on reported statistics on traffic accidents in Japan from the Cabinet Office (2007),
we define unit social costs as 229,032 thousand yen for the death of a victim and 5,044 thousand yen
for an injured victim.
4.2 Air Pollution
According to INFRAS/IWW (2004), as for the estimation method of the social costs of air
pollution, there are two approaches: top down and bottom up.
2

In this study, following Mizutani et

In Mizutani et al. (2011), type of victim is classified into three categories: (i) death, (ii) seriously
injured and (iii) lightly injured. However, statistics on highways show no distinction between seriously
injured and lightly injured, so that we had to use only two categories for statistics on victims.

6al. (2011), the bottom up approach, which calculates the social costs by examining, in order,
pollutants produced by vehicular transport, is chosen, as shown in equation-(4) to (8).

Cair ,a = ∑ Pair, g × POPair,a , g(4)g

POPair,a , g = f air, g ( ATM PM ,a )(5)

ATM PM ,a = atm PM ,a − atmback , PM(6)

atm PM ,a = α air, PM × EMI PM ,a

(7)
(8)

b
EMI PM ,a = ∑ (ERPM⋅Qab )bwhere,

Cair,a: Social costs of air pollution on highway – a caused by vehicular transport (yen),
Pair,g: Unit social cost of air pollution type- g (yen),
POPair,a,g : Number of victims of type – g on highway – a caused by air pollution (person),fair,g(・) : Exposed function by air pollution for type – g,
ATMPM,a : Annual concentration level of air pollution substances of PM10 caused by
vehicular transport on highway – a(µg／km3),
atmPM,a 3: Annual concentration level of PM10 (SPM) on highway – a,atmback,PM : Annual concentration level of PM10 caused by non-vehicular transport,
αair,PM : Parameter for the impact of PM10 by vehicular transport pollutants on surroundingarea per 1km2,
EMIPM,a : Annual amount of PM10 per area of 1km2 of vehicular transport pollutants on
highway – a (g/year),b

ER PM : Coefficient for pollution by PM10 by vehicular transport type-b (g/km)4,
Qba : Traffic volume of vehicular transport type-b on highway-a (vehicle-km),b : Vehicular transport type (b=1: passenger car,2: bus,3: small truck,

4: truck),5

g: Type of health damage by air pollution ,3

The data on this measure for each highway are not available, so we estimate this measure based on
the city’s annual concentration level of PM10. By regression analysis, we obtain the following
results.
atmPM,a = 0.023 + 0.00111EMIPM, a + 0.0051D（61.44） （2.91）(10.66)adjR2＝0.241
atmPM,a : Annual average concentration level of PM10 (SPM) in city – a (mg/km3),
2
EMIPM,a: Annual amount of PM10 per area of 1km of vehicular transport pollutants in city
– a (g/ m2/year),
D：Dummy of City in Pacific Ocean Belt Areas.

4

The coefficient for pollution by PM10 is obtained by using the calculation method of the Ministry of theEnvironment.

7

The unit social cost for this measure is based on Mizutani et al. (2011).
4.3 Noise
The social costs of noise are estimated by equation-(9) and (10).
into monetary value.

Noise is transformed

In this study, we modify the equation shown in the Doro Toshi no Hyoka ni

Kansuru Shishin Kento Iinkai (1998).

*
CdB,a = PdB ⋅ ( EMI dB,a − EMI dB) ⋅ POPdB,a(9)

POPdB,a = ∑ DISa,h ⋅ RdB ⋅ PDa,h

(10)

h

where,

CdB,a：Social costs of noise by vehicular transport on highway-a (yen),
PdB：Unit social cost of noise (yen/dB),
EMIdB,a：Noise level caused by vehicular transport on highway-a (dB(A))6,
EMIdB*：Standard noise level (50dB),
POPdB,a：Exposed population to noise level EMIdB,a (person),
DISa,h：Road length in surrounding area type-h on highway-a (km),
RdB：Affected areas exposed to noise (extension from the roadside of highway = 10m),
PDa,h：Population density in surrounding area-h on highway-a (person/km2),
h：Surrounding area (h=1: DID area, 2: non-DID area)
Again, the unit social cost for this measure is based on Mizutani et al. (2011).

4.4 Global Warming
The social costs of global warming are calculated by equation-(11) and (12).
(11)

Cwar,a = Pwar ⋅ EMICO2,a ⋅ TranCO2(12)b
EMI CO2,a = ∑ ERCO2,a
⋅Qab
b

€

where,

Cwar,a：Social cost of global warming caused by vehicular transport on highway-a,
Pwar： Unit social cost of emission of CO2（yen/t- CO2）,
EMIco2,a：Annual emission of CO2 on highway-a (g- CO2/year),5

Health damage caused by air pollution is classified into two major categories: mortality and morbidity,
as in the previous study by the European Commission (2005).
6 Noise level is estimated with equations based on the Doro Toshi no Hyoka ni Kansuru Shishin Kento
Iinkai (1998).

8

TransCO2：Transformation coefficient for ton unit of emission of CO2,
ERCO2,a,b：Coefficient for emission of CO2 by vehicular transport type-b on highway-a(g-CO2/km),b

Q a: Traffic volume of vehicular transport type-b on highway-a (vehicle-km),
b：Vehicular transport type（b=1：passenger car,2：bus,

3：small truck,

4：truck）.

As for the unit social cost for this measure, we assume that it is 1,233 yen/t- CO2.

This

cost is obtained from information from the European Commission (2005), in which the unit social
cost for this measure is 9 Euro/t- CO2 and the exchange rate is 137 yen/Euro.
4.5 Traffic Congestion
The social costs of traffic congestion are estimated in three steps.
to traffic congestion is estimated.

Time loss is specified as a function of traffic volume and road

length and speed, as shown in equation-(15).
calculated.

First, daily time loss due

Second, annual time loss due to traffic congestion isAs equation-(14) shows, congestion conditions on weekdays and weekends aredifferent, so we obtain the time loss separately.

Last, the monetary value of traffic congestion is

obtained, as equation-(13) shows.

(13)bCcon,a = ∑ Pcon
⋅ TLbabbb
TLba = tla,k=weekday ⋅ dw + tla,k= holiday ⋅ dh€€⎛ DISa ,i DISa ,i ⎞ btlab,k = ∑ ⎜⎜
− * ⎟⎟ ⋅ Qa ,i ,kVi ⎠
i ⎝ Va ,i
(15)
where

(14)
,

Ccon,a：Social cost of traffic congestion on highway-a (yen),
Pbcon：Unit social cost of time loss caused by traffic congestion of vehicle type-b on
highway-a (yen / minute-vehicle),b

TL a：Annual time loss caused by traffic congestion of vehicle type-b on highway-a(minute-vehicle/year),btl a,k：Daily time loss caused by traffic congestion on day type-k of vehicle type-b on
highway-a (minute-vehicle/day),dk：Number of weekdays and weekends per year, k = w(weekday), h(weekend)（dw＝246 days, dh＝119 days）,
DISa,i：Road length of observation point -i on highway-a (km),Va,i: Average speed at observation point-i on highway-a (km/h),
Vi*：Legally permitted maximum speed at observation point -i (km/h),9Qba,i,k：Traffic volume of vehicle type-b at observation point -i on highway-a (vehicle/day)b：Vehicular transport type（b=1：passenger car,2：bus,

3：small truck,

4：truck）

i：Observation point,
k：Weekday and weekend (k = w: weekday, h: weekend)

Again, the unit social cost for this measure is based on Mizutani et al. (2011).

5. Estimation Results of Social Costs of Highways
This section describes the structure of the estimated social costs of vehicular transport on
highways.

We focus especially on the following points: (i) the relationship between social costs

and traffic volume, (ii) the relationship between unit social costs per vehicle-km and traffic volume,and (iii) the structure and magnitude of social costs.
First of all, Figure 1 shows the relationship between the social costs of vehicular transport
and traffic volume.

The vertical axis is the social costs of highways.

measured as average numbers of vehicles per hour on highways.

The horizontal axis is

The most important finding is thatsocial costs increase at an accelerated rate as traffic volume increases.
per km of traffic volume, social costs seem to increase rapidly.

At around 3,000 vehicles

A similar finding with regard tocity size can be found in a study by Mizutani et al. (2011), which showed that cities with larger
populations produce larger unit social costs.
Second, there are variations in the details of social costs.

As for air pollution and noise,

distribution becomes much larger than for accidents and traffic congestion, which are more related to
the number of vehicles.
Figure 2 shows the relationship between unit social costs per traffic (vehicle-km) andnumber of vehicles per hour.

The relationship is not linear.

quadratic curve shows a gentler slope than is the case in Figure 1.

10

However, the fitted line by the(million yen)	
2,500
2,000
1,500
1,000
500
(number of vehicle
per hour)	
 0
0

500 1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

Figure 1 Relationship Between Social Costs of Vehicles and Number of Vehicles(yen/vehicle-km)	
60.00
50.00
40.00
30.00
20.00
10.00
0.00
0

500

(number of vehicle
per hour)	
1,000 1,500 2,000 2,500 3,000 3,500 4,000 4,500 5,000

Figure 2 Relationship Between Social Cost per Traffic and Number of Vehicles

11Third, the structure and the magnitude of social costs for whole highway networks areshown in Table 2.

From this table, we discern the following facts.

The largest component ofvehicular transport’s social costs on highways is traffic congestion, accounting for about 64%.
second largest component is traffic accidents, accounting for 24%.

The

Compared with these twocomponents, other components such as air pollution, noise and global warming make up only a small
percentage of costs.

In particular, air pollution resulting from a city’s transport accounted for 18 to

21%, according to Mizutani et al. (2011), but in the present study the air pollution component issmaller.

In general, highway speed is high and most highways connect cities in less populatedareas, so that social costs due to air pollution become smaller.
Table 3 shows the social costs of types of vehicles.

According to this table, the totalsocial costs of buses are the highest, based on vehicle-km, at about 16 times higher than for regularcars.

However, buses transport more passenger than regular cars, so that the figure would be lower

if based on passenger-km.

Trucks’ social costs are about 3 times higher than those of regular cars.

As for the magnitude of social costs of vehicles shown in Table 4, total social costs forwhole highway networks are about 678,212 million yen, or about 0.13% of Japan’s entire GDP.
Compared with highway fare revenues (1,083,600 million yen) and the operating costs of highways(687,770 million yen), social costs account for 62.6% and 98.6%.

Thus, the social costs of vehicles

on highways are almost the same as highways’ operating costs.

If we include both the operating

costs and social costs of highways, current fare revenues do not cover these costs.

If it isconsidered necessary to cover these costs, then highway fare should be increased.

Table 2 Estimated Social Costs of Highways

Total(million yen)
Per km(million yen)
Per vehicle-km
(yen)

Total

Traffic
Accidents

Air
Pollution

Noise

GlobalWarmingTraffic
Congestion

678,212(100.0%)164,460(24.2%)

15,727(2.3%)

32,349(4.8%)

32,466(4.8%)

433,210(63.9%)

83.63820.281

1.939

3.989

4.004

53.424

8.278

2.007

0.192

0.395

0.396

5.287

(Note):(1) These numbers are aggregate results of whole highway networks in Japan.
(2) Total network length of highways is 8,108.9 km and total vehicle-km is 81,932.
(3) Highway fare revenues in FY2005 for all highways are 1,083,600 million yen. And the operating
costs of highways (administration costs and depreciation) are 687,770 million yen.
(4) GDP in 2005 is 503,921 billion yen, based on IMF’s World Economic Outlook Database.
12

Table 3 Social Costs and Vehicle Type

Total

Traffic
Accidents

Air
Pollution

Noise

GlobalWarmingTraffic
Congestion

Car

6.50
(1.00)

1.99(1.00)

0.05(1.00)

0.82(1.00)

0.17(1.00)

3.48(1.00)

Bus

105.58(16.39)3.24(1.63)

3.40(68.00)2.71(3.30)

0.68(4.00)

96.55(27.74)

Small Truck

7.93(1.22)

2.65(1.34)

0.40(8.00)

0.82(1.00)

0.21(1.24)

3.85(1.11)

Truck

21.98
(3.38)

2.65(1.34)

3.55(71.00)2.46(3.00)

0.94(5.53)

12.37(3.55)(Note):(1) Unit: yen / vehicle-km(2) These numbers are the sample mean of 102 observations of highway networks.
(3) Total vehicle-km at the sample mean is 486 (car), 15 (bus), 86 (small truck), 217 (truck) million
vehicle-km.

Table 4 Magnitude of Social Costs

Total Social
Costs of
Highways

Total Fare
Revenues ofHighways

Total
OperatingCosts of
Highways

GDP in Japan

Total(million yen)

678,2121,083,600

687,770

503,921,000

Ratio of Total Social Costsof Highways to Each Item

1.000

0.626

0.986

0.001

(Note):(1) Fare revenues of highways are an aggregate of all highways in FY2005.
(2) Total operating costs of highways consist of administration costs and depreciation.
(3) GDP in 2005 is obtained from IMF’s World Economic Outlook Database.

13

6. Concluding Remarks
The main purpose of this paper is to estimate and evaluate the social costs of highways inJapan.

This study has several distinguishing points: 1) we estimate each individual highway’s

social costs by considering average speed at the peak period, total traffic volume, and types ofvehicular transport; 2) we distinguish five kinds of social costs of vehicular transport: (a) traffic
accidents, (b) air pollution, (c) noise, (d) global warming, and (e) traffic congestion; 3) we analyze
the relationship between the social costs of vehicular transport and traffic volume by using a data setof over 50 individual highways; and 4) we assess the magnitude of social costs by comparing with
GDP, highway fare revenues and the operating costs of highways.
Our findings based on the estimated results of social costs of highways are as follows.
(1) Social costs increase at an accelerated rate as traffic volume increases.

At around 3,000 vehicle

per km in traffic volume, social costs seem to increase rapidly.
(2) Accidents and traffic congestion are more related to number of vehicles than are air pollution andnoise.
(3) The relationship between unit social costs per traffic (vehicle-km) and number of vehicles is not
linear, but the fitted line by the quadratic curve shows a gentle slope.
(4) The largest component of vehicular transport’s social costs on highways is traffic congestion,accounting for about 64%.

The second largest component is traffic accidents, accounting for 24%.

(5) Compared with these two components, other components such as air pollution, noise and global
warming represent a small percentage of costs.
(6) Among vehicle types, buses’ social costs are largest at 105 yen per vehicle-km, about 16 times
higher than those of regular cars.
(7) Total social costs of whole highway networks are about 678,212 million yen, or about 0.13% ofJapan’s GDP.

Compared with highway fare revenues (1,083,600 million yen) and the operating

costs of highways (687,770 million yen), social costs equal 62.6% and 98.6%, respectively.

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