Y. Muromachi (% S. Yokoyama ^, N. Harata ^ & K. Qhta integration of travel demand management and...

The integration of travel demand management

and technological measures for reducing the

level of road traffic noise

Y. Muromachi (% S. Yokoyama ̂, N. Harata ̂ & K. Qhta ̂

(1) Engineering Research Institute, University of Tokyo, Japan(2) Department of Urban Engineering, University of Tokyo, Japan

(3) Institute of Environmental Studies, University of Tokyo, Japan

Abstract

Noise pollution is one of the major environmental damages caused byautomobiles. In 1997 of Japan, 4,135 out of 4,772 roadside observatory stationsfailed to keep environmental quality standards for noise. Since there has beenlittle improvement in the number of stations satisfying environmental qualitystandards, we need more powerful actions to change this undesirable situation. Inthis study, we constructed two models, traffic assignment model and traffic noisemodel, in order to test several policy measures of roads and road traffic forreducing the level of road traffic noise in a consistent way. The model was builton geographical information system (GIS) and it made the model moreoperational and easily understood. From a series of Sendai City case studies, theinstallation of drainage asphalt pavement proved an efficient way of decreasingthe level of traffic noise. Porous elastic road surface could abate traffic noiseconsiderably and would be a better measure if the cost would be reduced in future.Cordon pricing, as a measure of road traffic, was effective, but it also worsenedthe situation in the areas outside the cordon line. The construction of the ringroad relieved the serious situation in the city center, but still increased the level oftraffic noise in the areas around the cordon line since the ring road itself becamethe major traffic noise source. Finally the effects of the integrated measures ofroads and road traffic were tested and confirmed.

Urban Transport VI, C.A. Brebbia & L.J. Sucharov (Editors) © 2000 WIT Press, www.witpress.com, ISBN 1-85312-823-6

308 Urban Transport and the Environment for the 21st Century

1 Introduction

1.1 The trend of traffic noise pollution and proposed policy measures

Noise pollution is one of the major environmental damages caused byautomobiles. In 1997 of Japan, 4,135 out of 4,772 roadside observatory stationsfailed to keep environmental quality standards for noise [1]. The recent trend isshown in Figure 1. Since there has been little improvement in the number ofstations satisfying environmental quality standards, we need more powerfulactions to change this undesirable situation.

Japanese Environmental Agency proposed several policy measures forreducing road traffic noise pollution and we categorized them into four areas,vehicles, roads, road traffic and urban planning. While technological progresshas decreased the level of noise emitting from vehicles steadily for years, someinnovative measures in the area of roads, road traffic and urban planning havebeen at the stage of trial or initial implementation.

Policy measures of roads include noise barriers and innovative pavement aswell as new road construction. The effectiveness of noise barriers is shown inmany cases, but the application is physically limited to trunk roads with lessintersections. The effectiveness of new pavement, drainage asphalt pavement andporous elastic road surface, has been tested and confirmed recently. They not onlyreduce the generation of noise, but also absorb the generated noise considerably,though the cost is still higher. New bypasses and ring roads transferring thethrough traffic from the sensitive areas are also quite effective measures.

Policy measures of road traffic include travel demand management. Ascompared with capital investment such as new road construction, travel demandmanagement such as pricing could be more cost-effective if its effectiveness iswell understood and easily accepted by the people concerned.

1993

1994

1995

1996

1997

0% 20% 40% 60% 80% 100%

B Not Satifyingfor all periodsD Not satifyingfor any periodsE3 Satisfying for all periods

Figure 1: The percentage of observatory stations satisfying environmentalquality standards for noise in Japan from 1993 to 1997.


Urban Transport and the Environment for the 21st Century 309

Noise shielding by roadside buildings, transference of houses from theseverely polluted areas, and noise insulation by double-pane windows are allincluded in urban planning category. They are passive measures in themselves.Transference of houses in particular is generally regarded as a final action andthe number of cases is very limited due to its administrative cost. Japanese urbandevelopment control is so weak that new roads in a suburb are often absorbed intonew development instantly. The induced road traffic by the new development willcause serious noise problem around the new roads afterward.

1.2 The objectives of this study

Possible measures for reducing road traffic noise cover so many areas withdifferent merits and demerits that we need an integrated approach by which theeffectiveness of each measure can be evaluated in a consistent way. In this study,we constructed the initial integrated model that could take two out of fourcategories, measures of roads and road traffic, into consideration. The model wasbuilt on geographical information system (GIS) and it made the model moreoperational and easily understood. Following the brief review of precedingstudies, the structure of the model developed is explained in section two. Thepolicy analyses and their implications are presented and discussed in sectionthree. Then in the final section, conclusions and further studies are summarized.

2 Preceding studies

As Organization for Economic Co-operation and Development (OECD) [2]indicated, the problem of noise pollution caused by automobiles are common inmany countries and cities with heavy road traffic. In 1980s and 1990s, severalresearchers studied on the magnitude of the external cost of traffic noise as thepercentage of Gross Domestic Product (GDP). Verhoef, E. T. [3] summarizedthose studies and showed that the percentage of the external cost of traffic noiseranged from 0.02% to 11.18%.

One of the most ambitious studies of that kind conducted by Delucchi, M.& Hsu S. L. [4] estimated the external cost of road traffic noise about 0.002% to0.8% of Gross National Product (GNP) with a base case of about 0.05% in UnitedStates. They also reviewed the major determinants of the estimated value.According to their sensitivity analysis, important variables among others werethe change in house value per dB A, the ratio of the value of housing-units nearroads to the value of all housing units, annual interest rate, the housing-unitdensity, time spent away from home in places impacted by noise, threshold noiselevel and vehicle speed.

Those valuation studies generally concluded that the magnitude of theexternal cost of road traffic noise was not negligible, and that it should beinternalized by pricing and other policy measures. On the practicalimplementation of the proposed measures, we need more detailed models incirywide perspective since those studies were mostly based on nationwide analysis



Table 1. Several factors affecting the level of road traffic noise.(Y: modeled in this study, N: not modeled.)

itemstraffic

roads

surround ings

factorsvehicle typetraffic volumetraffic speeddri v i n g patterntravel demand functionstructurepavementnoise barr ieratmospheric conditionstopographic conditionsbui Id ingsground covers

YYYNYNYYNNNN

itemsreceptors

evaluation

factorspopulation densityact ivityhous i ngsubtend ing b u i l d i ngsnoise insulationnoise damage functionthreshold noise valuehousing value per dBAWTA/WTPannual interest rate1 i fet i me of hous i ngthe cost of measures

YYNNNYNNNNMY

and lacked in clear relationship between policy measures and their effectiveness.Moriguchi, Y, Nishioka, S. & Shimizu, H. [5] and Hayashi, Y., Kato, H.,

Mochizuki, N., Kojima, T. & Nakai, K. [6] were early examples of regionalmodels that could take road traffic noise pollution into account. Those modelswere so comprehensive that the part of traffic noise pollution constituted onesub-model of total system. Mayeres, I., Ochelen, S. & Proost, S. [7] constructed alarge-scale model for evaluating the marginal external costs of urban transport.The sub-model of traffic noise pollution in a simple form was responsive topricing and other policy measures. Although the research purpose of Watanabe,Y. & Honda [8] was different from ours, their traffic noise model applied to amixed residential zone could also be useful for a citywide analysis.

Table 1 shows the factors affecting the level of road traffic noise pollution.Some of those factors were modeled in this study, but others were not due to thedata availability and time constraint. Some variables for economic evaluationwere omitted because this study was not oriented toward estimating the absolutevalue of the external cost of noise pollution caused by automobiles.

3 The structure of models

3.1 The characteristics of the study area and the structure of models

As a study area, we selected Sendai City, a Japanese city located in 350km northof Tokyo. The population of Sendai City was about one million and that ofmetropolitan area was about 1.5 million. Traffic Census of 1994 and DigitalRoad Map of 1995 allowed us to analyze the vehicle trip distribution pattern andthe hourly traffic volume on major road network. There are about twenty roadsideobservatory stations for road traffic noise located within 5 to 45 meters from theroad edge in Sendai City. The datasets from those stations were used for modelvalidation. Population Census of 1990 and Establishment Census of 1991 in theform of approximately 500 meter square mesh enabled us to see the sensitivity of



2,000 - 30.000H 1.500 - 2.000H 1.000 - 1.500d 500 - 1.000D 0 - 500

Figure 2: Daytime population density distribution in Sendai City.

each mesh to road traffic noise pollution in the daytime as well as in thenighttime. Figure 2 shows daytime population density distribution in Sendai City.

We constructed two models, traffic assignment model and traffic noisemodel. Traffic assignment model estimated hourly traffic pattern on major roadnetwork, while traffic noise model estimated the number of people exposed to acertain level of road traffic noise.

3.2 Traffic assignment model

The inputs of traffic assignment model were fixed OD matrices of each vehicletype and the outputs were hourly traffic volume and average traffic speed onmajor roads. BPR performance functions relating traffic volume with averagetraffic speed were adopted with minor adjustments to Japanese situation [9].Stochastic user equilibrium assignment approach [10] assuming the situationwhere "no motorist can improve his or her perceived travel time by unilaterallychanging routes" was applied repeatedly for 24 hours. For converting money costinto time cost on expressways, we used 56/90/101 yen per minute forcars/pickups&vans/trucks as value of time respectively, which the ProvisionalGuidelines for Road Investment Assessment in Japan [11] proposed.

The correlation between observed and estimated value of traffic volume onmajor roads was 0.79, while that of average traffic speed was 0.77. Althoughsystematic errors and different standard errors among vehicle types still remained,we left the improvement of the traffic assignment model for further studies. Inaddition, our model outputted only average traffic speed on major roads andcould not take the driving patterns of acceleration, deceleration and idling intoaccount, which also needed further research.



3.3 Traffic noise model

The inputs of traffic noise model were traffic volume and average traffic speed onmajor roads estimated from the traffic assignment model, in addition topopulation density distribution. The output was the number of people exposed toa certain level of road traffic noise. Because Japanese Environmental Agency hasintroduced the equivalent sound level (LAeq) as a measure for environmentalquality standards for noise since April 1999, we evaluated the level of trafficnoise by L*eq. Before the introduction, 50 percentile level (L$o) had been used as ameasure, so we used it for the validation of our traffic noise model. Table 2 showsnew environmental quality standards. The basic traffic noise model for L*eqproposed by Acoustical Society of Japan (ASJ) [12] is shown below.

,̂=101og,,,-£,10̂ '""-A/,. (1)

where :TO = unit time (s)LpA(,i) = the sound pressure level (of the /th road segment)

Ar,-= 1/traffic speedN = hourly traffic volumeLWA = the average sound power level of vehiclesr = the distance between the source and the receptorL = correction factor

Although ASJ proposed the models that could consider atmospheric andtopological conditions, the relative heights of the road and receptors, drivingpatterns, and the shielding by intervening structures, we neglected those factorsin our model because of data availability. The effects of installing specificpavement and noise barriers as policy measures of roads were evaluated in asimpler way in the next section.

Each mesh was divided into 2,500 smaller grids (approximately 10 metersquare) and the level of road traffic noise was predicted for each representativegrid. Assuming that population density was distributed evenly among all gridswithin the same mesh, we estimated the number of people receiving a certainlevel of traffic noise by aggregating the population of each grid by traffic noiselevels. The correlation between observed and estimated value of traffic noisealong major roads was 0.71, which might not be enough for assessing the effectsof a particular project, but still useful for comparing the merits and demerits of

Table 2. New environmental quality standards for noise.

New Envi ronmentExclusive residential aResidential areas nearMixed residential areasAreas close to highwaysAreas close to highways

al Qual ity Standarreas near roads withroads with one lanenear roads with two

(indoor)

ds in LAeqtwo lanes or more

or morelanes or more

6:00-22:006065657045

22:00-6:005560606540



Current Total Noise Damage

2.000 - 30.0001.500 - 2.0001.000 - 1.500

H 500 - 1.000D 0 - 500

Figure 3: Current total noise damage (TND).

several policy measures for reducing road traffic noise pollution in city-wideperspective.

The distribution of the number of people by traffic noise levels wasestimated from the traffic noise model. In the nighttime of Sendai City, the shareof the people exposed to traffic noise over 55 dB(A) was estimated less than tenpercent since the vehicles on major roads were very few at night. In the daytime,the share over 60 dB(A) was more that thirty percent. Considering this situation,we focused on the daytime traffic noise pollution. We defined the city-wide indexof traffic noise damage (TND) as follows,7WD = (Af-60)*fOf (2)where :A^ = traffic noise level (dB(A))POP = the number of people exposed to N level of traffic noise

Figure 3 shows the distribution of TND in the daytime of Sendai City. Thefigure indicates the city center as well as the areas near the expressways wasdamaged most by road traffic noise pollution.

4 Policy analyses and their implications

4.1 Policy measures of roads

First, we evaluated the effects of policy measures of roads, the installation ofnoise barriers, drainage asphalt pavement and porous elastic road surface. Weassumed all expressway segments would be equipped with noise barriers whosesize was 3m in height and 53km in total length. The effect of 10 dB(A) reductionwith the cost of 50,000 yen per nf was also assumed. As to the new pavement,the roads whose 12 hour traffic volume was over 5,000 were selected for theinstallation, 214km in total length. The effect of 2-3dB(A) with the cost of 2,200



yen per nf for drainage asphalt pavement and the effect of 6-9 dB(A) with thecost of 25,000 yen per nf for porous elastic road surface were assumed.

Table 3 indicates the percentage of reduction by each measure from thecurrent TND. We also calculated the benefit/cost ratio based on 4% social interestrate, 40 year life for noise barriers and 3 year life for the new pavement, and20,000 yen per dB(A) per year benefit quoted from the Provisional Guidelines forRoad Investment Assessment. While the installation of porous elastic roadsurface reduced the current TND most, that of drainage asphalt pavement abatedit more efficiently because it was less expensive. The benefit/cost ratio for noisebarriers was low due to the low daytime population density around theexpressways.

Table 3. The effects of policy measures of roads.

sound barriersdrainage asphalt pavementporous elastic road surface

% reduction in TND1

1968

727

benefit/cost ratio0.2.0.

556884

4.2 Policy measures of road traffic

Second, we tested the effects of cordon pricing as policy measures of road traffic.The cordon line was set along the planned ring road within about 3km from thecity center. Three charging cases, 200, 400, and 600 yen per trip crossing thecordon line were compared. Table 4 summarizes the results of three areas, innercordon, around the cordon line and outer cordon (within 6km from the citycenter) as well as the results of total.

As the charging price increased, traffic volume within the city centerdecreased and the TND there also reduced. In total, however, only marginalreduction in TND was predicted since the diverted traffic avoiding chargesdeteriorated the level of traffic noise pollution in outer cordon areas and offset thegain in the city center. The lack of ring road also worsened the situation.

Table 4. The effects of policy measures of road traffic.

% reduction in TNDcordon pricing 200 yencordon pricing 400 yencordon pricing 600 yen

inner9.5

13.117.6

around7.57.37.2

outer-1. 1-2. 1-3.8

total6.48.6

11.2

4.3 Integrated measures of roads and road traffic

Finally, we tested integrated approach combining measures of roads and roadtraffic. The previous section suggested if cordon pricing was implemented, thering road should be constructed simultaneously. The results of this case,assuming the cost of ring road 4 billion yen per km, are indicated in Table 5. Ascompared with the total TND of cordon pricing (600 yen) without the ring road,the total TND with the ring road reduced more, but considerable counter-effectsaround the cordon line remained since the ring road itself became the major



traffic noise source. We tested further two cases of cordon pricing with the ringroad covered with drainage asphalt pavement and porous elastic road surface. AsTable 5 shows, the latter integrated measure was successful in reducing the levelof road traffic noise in the areas around the cordon line as well as the level in thecity center. According to the benefit/cost ratio, drainage asphalt pavement wasbetter because the cost was less expensive. Figure 4 shows the rate of change fromthe current TND for the final case with porous elastic road surface.

Table 5. The effects of integrated policy measures of roads and road traffic.

% reduction in TNDA. cordon pricing 600 yenB.A+ring roadC.B+drainage asphalt pavementD. B+porous elastic road surface

inner17.625.925.925.9

around7.2

-103.0-52. 135.6

outer-3.8-0.3-0.3-0.3

total11.213.815.618.6

Figure 4: The rate of change in TND by the integrated policy measures.

5 Conclusions and further studies

In this study, we constructed two models, traffic assignment model and trafficnoise model, in order to test several policy measures of roads and road traffic forreducing the level of road traffic noise in a consistent way. From a series ofSendai City case studies, the installation of drainage asphalt pavement proved anefficient way of decreasing the level of traffic noise. Porous elastic road surfacecould abate traffic noise considerably and would be a better measure if the costwould be reduced in future. Cordon pricing, as a measure of road traffic, waseffective, but it also worsened the situation in the areas outside the cordon line.The construction of the ring road relieved the serious situation in the city center,but still increased the level of traffic noise in the areas around the cordon linesince the ring road itself became the major traffic noise source. Finally the effects



of the integrated measures of roads and road traffic were tested and confirmed.The traffic assignment model and the traffic noise model developed in this

study were at the initial stage and left much to be improved. The omission of thevariables describing the driving patterns might underestimate the level of trafficnoise, while the exclusion of the effects of subtending by buildings and noiseinsulation might overestimate it. Those factors as well as others should beincluded for further studies.

References

[1] Japanese Environmental Agency. Roadside Traffic Noise No. 10(m Japa/?f,?fA 1998.

[2] Organization for Economic Co-operation and Development. Transport andthe Environment, 1988.

[3] Verhoef, E. T. External effects and social costs of road transport.rm/7%?orfafm/7 #e.ffarc/? 28A(4), pp.273-287, 1994.

[4] Delucchi, M. & Hsu, S. L. The external damage cost of noise emitted frommotor vehicles. Journal of Transportation and Statistics 1(3), pp. 1-24, 1998.

[5] Moriguchi, Y., Nishioka, S. & Shimizu, H. Development of simulationprogram for assessing the improvement of environmental impacts bycountermeasures on regional traffic pollution (in Japanese). InfrastructurePlanning Review 11, pp.279-286, 1993.

[6] Hayashi, Y., Kato, H., Mochizuki, N., Kojima, T. & Nakai, K. Developmentof a user-friendly landuse-transport-environment analysis tool (in Japanese).Proceedings of Infrastructure Planning 19(1), pp.321-324, 1996.

[7] Mayeres, I., Ochelen, S. & Proost, S. The marginal external costs of urbantransport. Transportation Research 1D(2), pp. 111-130, 1996.

[8] Watanabe, Y. & Honda, A. A calculation method of environmental capacitynear trunk roads to meet the Japanese environmental quality standard fornoise annoyance under various conditions (in Japanese). InfrastructurePlanning Review 14, pp.443-449, 1997.

[9] Matsui, H. & Yamada, S. Estimation of the BPR functions by using roadtraffic census data (in Japanese). Traffic Engineerig 33(6), pp.9-16, 1998.

[10] Sheffi, Y. Urban transportation networks, Prentice-hall, 1985[11] The Committee for Guidelines for Road Investment Assessment. Provisional

Guidelines for Road Investment Assessment (in Japanese), 1998.[12] Acoustical Society of Japan. ASJ model 1998 (in Japanese). Journal of

55(4), pp.281-324, 1999


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