development of an assessment framework for green highway construction

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Development of an assessment framework for greenhighway constructionRong‐Yau Huang a & Cheng‐Hung Yeh b

a Institute of Construction Engineering and Management , National Central University,Jhongli City , Taoyuan 32001, Taiwan, R.O.C. Phone: 886–3–4227151 # 34108 E-mail:b Institute of Construction Engineering and Management , National Central University,Jhongli City , Taoyuan 32001, Taiwan, R.O.C.Published online: 04 Mar 2011.

To cite this article: Rong‐Yau Huang & Cheng‐Hung Yeh (2008) Development of an assessment framework for greenhighway construction, Journal of the Chinese Institute of Engineers, 31:4, 573-585, DOI: 10.1080/02533839.2008.9671412

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Journal of the Chinese Institute of Engineers, Vol. 31, No. 4, pp. 573-585 (2008) 573

DEVELOPMENT OF AN ASSESSMENT FRAMEWORK FOR

GREEN HIGHWAY CONSTRUCTION

Rong-Yau Huang* and Cheng-Hung Yeh

ABSTRACT

The objective of this research is to develop a framework for the assessment ofgreen highway projects. Highway construction is chosen from among the varioustypes of large-scale infrastructure because they cover broad areas and take up a largeshare of a nation’s infrastructure development. After completing a literature reviewwe employ the Max-Min Fuzzy Delphi method to identify the major categories andtheir corresponding items most suitable for assessing the “greenness” of a highwayproject. The five major categories identified are: preservation of the eco-system, plan-tations to reduce CO2 emission, preservation of material resources, waste reduction,and water conservation. The Analytical Hierarchy Process (AHP) is then employedto determine the weighting of the major categories as well as the sub items in eachcategory. The end result is an assessment rating framework to assess the “greenness”of a highway construction project.

Key Words: highway, sustainable, green, construction, assessment.

*Corresponding author. (Tel: 886-3-4227151 # 34108; Email:[email protected])

The authors are with the Institute of Construction Engineeringand Management, National Central University, Jhongli City,Taoyuan 32001, Taiwan, R.O.C.

I. INTRODUCTION

Major changes in the world’s environment andclimate over the last few years have brought alarm-ing portents for human civilization pointing out thatthe world enviroment is under siege. Climate shiftsare finally making mankind realize the hidden costsof squandering the earth’s resources. The concept of“sustainable development” which emphasizes thecoexistence of global development with the environ-ment and ecology, is gradually taking hold aroundthe world. One of the key areas of global environ-mental protection work at this point in time is theimplementation of sustainable development indica-tor systems to evaluate problems in various industries.

Highway projects are closely linked with people’severyday lives. They play an essential role in a nation’ssocial and economic development. In Taiwan, the sta-tistics (Lin, 2003)indicate there are approximately 37,299 km of road, of which urban roads constitute roughly16,483 km and the highway system constitutes roughly

20,816 km. In the past, most highway projects havebeen geared towards promoting economic developmentand creating jobs. Therefore, throughout the stagesof planning, design, construction, maintenance, andreplacement, the impact of such aspects as routeselection, road type design, working methods, and choiceof materials on the natural environment has been com-monly neglected. For instance, it is a challenge to achievebalance between the grade of the road and the routedesign, often making it necessary to perform exten-sive excavation and filling. The impermeable asphaltand concrete used to pave roads can alter the absorp-tion of water by the ground and affect the soil’s waterstorage ability. The construction process also oftenproduces large amounts of waste and pollution and,finally, construction of the roadbed, foundation layer,and road surface consumes large quantities of naturalsand and gravel.

Today’s thinking on road construction is focusedon addressing the issues of how to harmonize trans-portation needs with local ecological protectionconsiderations, how to avoid subsequent environmen-tal destruction and excessive resource consumption,and how to incorporate sustainable development con-cepts into highway projects. This study explores thevarious aspects and factors involved in this so-called“green highway construction”, analyzes the relative

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574 Journal of the Chinese Institute of Engineers, Vol. 31, No. 4 (2008)

importance of the various factors, and establishes apreliminary assessment framework intended to lessendisturbance of the natural environment, and to strikea balance between project construction and sustain-able development. It is hoped that this work will makea contribution to the application of sustainable de-velopment to highway construction.

II. LITERATURE REVIEW

1. Sustainable Development and Sustainable Con-struction

The concept of “sustainable construction”, whichis also known as “green construction” in Taiwan, isderived from the concept of sustainable development.The “Brundtland Report” issued by the World Com-mission on Environment and Development (WCED) in1987 (The Brundtland Report, 1987) defined sustain-able development as “development which meets theneeds of the present without compromising the abilityof future generations to meet their own needs.” TheBrundtland Report, however, does not specificallymention sustainable development in relation to

construction. It was not until the formulation of “Agenda21” from the 1992 Earth Summit that several issuesconnected with the category of construction werediscussed; these issues included sustainable use of land,residential energy consumption, transportation problems,waste reduction and disposal, and so on.

Sustainable construction is taking different di-rections in different countries, reflecting differing na-tional sentiments. Nevertheless, while sustainableconstruction may be defined differently from place toplace, all definitions contain certain points of agreement.Some definitions of sustainable construction from variouscountries, including the Netherlands (CIB, 1999), USA(Kibert, 1994), Finland (Huovila, 1999), Taiwan (Huangand Kou, 2002; Architecture and Building ResearchInstitute, 2003; Yu et al., 2002) and Japan (Chang etal., 2000), are compiled in Table 1. All of these defi-nitions implicitly take into consideration the aspect ofhuman health and comfort, while also emphasizing thereduction of environmental impact. The definitionsof the Netherlands and Taiwan also contain the item“making full use of resources.”

In this study we term highway construction projectsthat comply with the principles of sustainable or green

Table 1 Definitions of sustainable construction

Country Definition

• Environmentally friendly construction achieving sustainable coexistence with thenatural environment throughout the stages of planning, design, construction, andservice life, and stressing environmental ethics including consumption of minimalenergy and resources, harmony with the environment, and sharing with latergenerations.

• Architectural design geared towards human health and comfort, pursuing coexist-ence with the global environment, and fostering the sustainability of the people’sliving environment.

• Buildings should consume relatively few natural resources and manufacture rela-tively little waste.

• The creation and responsible management of a healthy man-made environment basedon the efficient use of resources and ecological principles.

• In the process and during the service life of the structures, aims at minimizing theuse of energy and emissions that are harmful for environment and health, and givesrelevant information to the consumer for enlightened decision making.

• Official definition: a way of building aimed at reducing the impact on health andenvironment by the construction process, by the building, or by the built-upenvironment.

• More precise definition: the reduction of the use of natural resources and the con-servation of the life support function of the environment under the premise that thequality of life is maintained

• Low environmental impact, high contact with the environment, amenities and health.

Source: References (Huang and Kou, 2002; Architecture and Building Research Institute, 2003; Kibert, 1994; Huovila,1999; CIB, 1999; Chang et al., 2000); adapted for this study.

Taiwan(green construction)

(Huang and Kou, 2002)

Taiwan(green architecture)

(Architecture and BuildingResearch Institute, 2003)

1st Internationalconference on sustainable

construction (Kibert, 1994)

Finland(sustainable construction)

(Huovila, 1999)

Netherlands(sustainable construction)

(CIB, 1999)

Japan(environmentally-friendly

buildings)(Chang et al., 2000)

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R. Y. Huang and C. H. Yeh: Development of an Assessment Framework for Green Highway Construction 575

construction, “green highway construction,” in linewith the foregoing definition.

2. Key Aspects of Green Highway Construction

To date, most attention and effort in the devel-opment of sustainable construction in countries allover the world has been devoted to buildings. Al-though the experience and knowledge acquired in theprocess of developing sustainable or “green” build-ings is certainly of some help in devising ways to fa-cilitate green highway construction, very limitedmention can be found in the literature on the assess-ment of green highway construction. In Taiwan, thesomewhat successful experience of promoting greenbuildings has also prompted the government to payattention to green highway construction, since a bigchunk of the annual national budget has been spenton the highway infrastructure.

Existing Taiwanese studies of green highway con-struction address the subject from different angles.Chiu (2002) and Shen (2001) explore environmentalconsiderations throughout the stages of the projectlifecycle, including feasibility research, planning,design, construction, maintenance, and management;their environmental considerations are listed in Table2. Hsieh and Lin (2004) investigate implementationstrategies of ecological construction techniques for

different road components, which include slopestabilization, drainage, bridges, tunnels, culverts,railings, lighting, traffic control, service areas, andinterchanges. For their part, Huang and Kou (2002)look at things from the three sides of environment,society, economy. They use 10 assessment items:natural conservation, energy conservation, water/soilconservation, waste reduction, revegetation, materials,safety & comfort , fair development, culturalpreservation, and cost-effectiveness to perform sum-mary assessments of different types of projects. Whilethe aspects considered by the latter two researchersare completely in line with the spirit of sustainabledevelopment, they are not specifically connected withroad construction. In addition the social and economicsides of their assessment framework lack objectiveassessment methods, making it difficult to performan accurate assessment. Chen, Chou and Yu (2001)classify project types as: roadways, railways, watersides,slopes, and draft valuation indicators for the threeassessment categories: the environment, ecology, andresources. For each assessment aspect, there are 15valuation indicators.

The foregoing review of the literature reveals thatthere is a complex array of environmental factors thatneed to be taken into consideration in road construc-tion projects, and each stage in a project life cycle hasa different impact on the environment. In this study

Table 2 Environmental considerations at each stage of the project life cycle

Stage of theproject life Environmental considerations

cycle

Survey of environmental status, assessment of selected route.

Nature of the ecological environment, water resource protection zones, landforms,geology, drainage, permeability, wildlife habitat, animal migration routes, plantcommunities, and special natural and man-made scenery.

Selection of road structure, animal migration route considerations, roadside barrierfacilities, effect of road lighting on the peripheral environment, habitat relocationand development, topsoil reuse, ecological functions of drainage corridors, selectionof side slope form, ecological landscaping, landscaping, water conservation, coexist-ence with the environment, energy conservation, carbon dioxide reduction, wastereduction, environmental protection, scenic improvement, protection of livingenvironment, maintenance of traffic safety, drainage, maintenance, common channels,auxiliary facilities, and resource recycling and reuse.

Highway construction work content and environmental disturbance, environmentalconsiderations in project plans, construction road selection and environmentrestoration, construction drainage rerouting and water pollution control, noise control,construction dust pollution control, other construction precautions, such as for noise,water, vibration, waste, and fill/spoil.

Maintenance and management plan for overall ecological considerations, use of amulti-stage environmental monitoring plan.

Source: References (Chiu, 2002; Shen, 2001); adapted for this study.

Feasibility research

Planning

Design

Construction

Maintenanceand

management

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we classify valuation indicators in the literature thatare similar in nature and apply the green architecturecertification framework, which has been successfullyimplemented in Taiwan, to the indicators for green high-way construction. Care is taken to comply with theprinciples of simplicity, clarity, and technical feasibility.The six aspects or categories utilized as green high-way construction assessment topics are “ecology”,“landscaping”, “materials”, “waste reduction”, “wa-ter conservation”, and “energy conservation”; indica-tors are established for each aspect for use in actualassessment work. For example, there are five valua-tion indicators within the ecological category, fivevaluation indicators within the landscaping category,four valuation indicators within the materials category,four valuation indicators within the waste reductioncategory, four valuation indicators within the waterconservation category, and three valuation indicatorswithin the energy conservation category. This makesa total of 25 valuation indicators (see Table 3 for details)which make up the framework of a prototype assess-ment system.

III. ASSESSMENT FACTOR SELECTIONQUESTIONNAIRE SURVEY AND ANALYSIS

In this study we first apply the fuzzy Delphi method(FDM) to determine the appropriateness of the vari-ous factors. The conventional Delphi method has thedisadvantages of slowness, high cost, and restrictingspecialist opinions within a circumscribed scope (Hsu,1998; Chu, 2004). However Ishikawa (1993) usedthe concepts of cumulative frequency distribution andfuzzy integrals to integrate specialist opinions as fuzzynumbers, in what is called the fuzzy Delphi method.FDM offers the following advantages: (1) Full ex-pression of specialists’ opinions with a lower surveyfrequency. (2) The inevitable fuzziness of the inves-tigation process is taken into consideration. The max-min fuzzy Delphi method proposed by Ishikawa isemployed to select the assessment factors in the firststage; these selected factors serve as the basis forprofiling and weighting evaluation in the second stage.

1. First-Stage FDM Questionnaire

Based on the literature review we classify thefactors for green highway construction assessment into25 items in the six categories of ecology, landscaping,materials, waste reduction, water conservation, andenergy conservation (Table3). This is used to estab-lish a preliminary framework for the first-stage FDMquestionnaire. After selecting the items and factorswith a certain degree of importance, we establish avaluation indicator framework. A total of 35 specialistsparticipated in the first-stage FDM questionnaire

including eight academics, four government agencyspecialists, and 23 industry specialists, with an aver-age of ten years of seniority; see Table 4.

In the following section we outline the steps ofthe FDM for the assessment of the ecology categoryasan example:

Step 1: Establish the cumulative frequency distribu-tion function for the value with the greatestdegree of agreement (F1(x)) and the valuewith the least degree of agreement (F2(x)).

Tabulate the returned questionnaires to yield eachspecialist’s importance assessment value for each eco-logical factor, including the “minimum acceptable value”and “maximum acceptable value.” The assessmentvalues for ecological factors are shown in Table 5.

Step 2: Calculate the “first quartile,” “median quartile,”and “third quartile” for F1(x) and F2(x); substi-tute (D1, M1, C1) and (D2, M2, C2).

From the cumulative frequency of the maximumand minimum values of F1(x) and F2(x) shown inTable 5, we can see that the “first quartile,” “medianquartile,” and “third quartile” of F1(x) and F2(x) areF1 (C1, M1, D1) = (8, 9, 10) and F2 (D2, M2, C2) =(8, 6, 5).

Step 3: The point of intersection between (C1, M1,D1) and (D2, M2, C2) is the target importancevalue X*.

The arithmetic mean of C1 and D2 is taken asthe point of intersection between F1(x) and F2(x), orX*, In this way we find that ecological factor X* =(C1+D2)/2 = (8 + 8) / 2 = 8, which means that itsimportance level is 8. The importance values of theother factors were calculated similarly, and the re-sults are shown in Table 6.

In the literature, 7 is the most commonly usedvalue for the selection threshold for the various as-sessment values. We also used a value of 7 as theselection threshold. In other words a factor is selectedwhen X* is greater than 7. Table 6 shows the selec-tion results. The grey background indicates factorsthat did not pass the first-stage of the selection process.The results were then used as assessment factors duringthe AHP weight calculations in the second stage.

2. Analysis of FDM Questionnaire Results

The X* value distribution of the various factorsfrom the questionnaire results was in the range of 5.5~8. Among the major factors, ecology and landscapingwere highest with 8, and materials, waste reduction, and

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Table 3 Highway construction environmental impact factors as classified in this study

Description

Pre-construction environmental survey, selection of highway corridor.

Survey of existing animal habitat and relevant protective and compen-satory measures.

Topsoil preservation and reuse measures during development process.

Apart from performing drainage functions, the drainage corridor shouldcontain porous vegetated ditches.

Environmental monitoring measures should be used after the comple-tion of the project to keep tabs on the actual effect of the project on theenvironment and ecology, and determine the effectiveness of theadopted ecological protection measures.

Landscaping should adopt an ecologically sound approach, for examplethe selection of a diversity of tree species to avoid the establishmentof a monoculture and shrubs should be planted on exposed soil be-neath trees.

Vegetation should cover a certain percentage of land able to sustainplants.

Plants able to sequester large amounts of carbon should generally bethe first preference. Plants such as grass and bedded flowers with poorcarbon sequestration capacity should be planted sparingly.

Endemic plant species found in the site’s environmental survey shouldbe planted as a first preference; preference should also be given tobird- and butterfly-attracting plants species in order to provide foodand shelter for other organisms.

Possible vegetation should be restored in accordance with the resultsof the site environmental survey.

Recycled materials should be adopted as a first preference duringdesign.

Projects should give wood or other materials with a low environmen-tal load first preference during design.

Measures and equipment should be easy to remove and maintain, so asto reduce consumption of labor and resources during the maintenanceand management stage.

Highly durable materials should be used in order to lessen the need forreplacement and maintenance throughout the project life cycle.

The road structure should be reviewed after confirming the roadcorridor. The adopted structure should minimize disturbance to theoriginal ground and scenery.

Automated working methods including the use of pre-cast elements,system templates, and non-shored bridges should be given preference.

Prevention and recycling measures should be adopted to control wasteproduced by the construction process (such as wastewater and dust).

Large-scale excavation and backfilling operations should be avoidedwhenever possible. If this is not possible, a balance should be achievedbetween the minimum excavation area and the shortest transportdistance.

Aspect

Ecology

Landscaping

Materials

Wastereduction

Indicator

Survey of existingenvironment

Destruction of animalhabitat and migrationroutes

Topsoil preservationand reuse

Ecological functionsof drainage corridor

Environmentalmonitoring measuresafter projectcompletion

Diversified andmultilevel landscaping

Vegetation coverage

Carbon sequestration

Endemic and bird- andbutterfly-attracting plants

Restoration of possible veg-etation

Use of recycled buildingmaterials

Use of environmentally-friendly materials

Measures and equipmentthat are easy to maintain andmanage

Application of durablematerials

Use of a road structurethat minimizesdisturbance to theoriginal ground andscenery

Selection of automatedworking methods

Pollution control during theconstruction process

Minimization of excavationand earthmoving

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Table 4 Background of the specialists participating in the first-stage FDM questionnaire

Number AverageSpecialist

Organization Position of years ofclassification

persons seniority

Feng Chia University, University of Chinese Professor,Culture, National Central University, Associate

AcademicNational Taipei University of Technology, Professor 8

specialistsNational Taiwan University of Science andTechnology

Tainan County Government, AssistantGovernment Miaoli County Government, Engineer, Senior

agency National Expressway Engineering Engineer, 4specialists Bureau Technician, 10

Consultant

Sinotech Engineering Consultants Ltd., Engineer,Jeyuehchen Engineering Consultants Ltd., Planner,Tingchiang Engineering Consultants Ltd., Architect,

IndustryGenesis Engineering Consultants Ltd., Landscape 23

specialistsGreen Empire Industrial Co., Ltd. Designer,

EnvironmentalPlanner

Table 5 Cumulative frequency table for maximum and minimum assessment values of the ecologicalfactors

Assessment values 1 2 3 4 5 6 7 8 9 10

Frequency of appearance of maximum value (max) 0 0 0 1 0 2 3 6 9 14F1: Cumulative frequency of maximum value 0 0 0 1 1 3 6 12 21 35Frequency of appearance of minimum value (min) 0 0 2 2 4 4 7 7 8 1F1: Cumulative frequency of minimum value 35 35 33 31 27 23 16 9 1 0

Table 3 Highway construction environmental impact factors as classified in this study (continue)

Description

Side slope shapes should consist of embankments and artificial hillsas a first preference. Roadcut side slopes should generally be pro-tected using free mesh screens or RC screens. Use of shotcrete slopeprotection should be avoided so as to ensure water permeability.

To lessen surface runoff, asphalt road surfaces should have a water-permeable pavement design whenever possible.

A direct infiltration design employing ground infiltration drainage pipesand drywells can increase the road corridor’s water conservation ability.

A surface water storage infiltration design or subsurface gravel infil-tration design can increase the road corridor’s water conservationability.

The road design should feature smooth slopes.

Energy conservation facilities should be employed to avoid unneces-sary energy waste.

Energy should be obtained from natural sources such as wind power,waste heat from incinerators, etc. whenever possible.

Aspect

Waterconservation

Energyconservation

Indicator

Use of highlywater-permeable sideslope shapes

Water-permeable pavementdesign

Direct infiltration design

Water storage infiltrationdesign

Effect of road grade onvehicle energyconsumption

Use of energyconservation facilities

Use of natural energy orreuse of waste heat

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water conservation had values of 7, all of which wereabove the threshold of 7. However, the X* value ofenergy conservation was lowest at 5.5 so it failed tomeet the threshold. Among subfactors, the three itemsof survey of existing environment, vegetation coverage,and use of highly water-permeable side slope shapesshared the highest X* value of 8. Subfactors that failedto meet the threshold included the six items of use ofdurable materials and measures and equipment that iseasy to maintain and manage in the materials category,direct infiltration design in the water conservationcategory, and the effect of the road grade on vehicleenergy consumption, use of energy conservationfacilities, and use of natural energy or reuse of wasteheat from the energy conservation category.

In summary, the major factor, energy conservation,

and its three subfactors, all failed to meet this study’simportance value threshold of 7. This indicates thatenergy conservation has less importance in the as-sessment of green highway construction than otherfactors. As for why this should be, Taiwan currentlyhas relatively little notion of road energy conservation,and lacks the technology needed to make improve-ments in this area. Unlike energy conservation inbuildings, where changes in architectural design canlead to tangible results, for example by cutting downon lighting and air conditioning needs, road constructionpersonnel are unfamiliar with the concept of energyconservation. The subfactors use of durable materi-als and measures and equipment that is easy to main-tain and manage, which both failed to meet the threshold,are connected with road maintenance. The use of

Table 6 FDM importance value of factors in each level

Major factor Sub-factor C1 C2 D1 D2 X*

Ecology 8 5 10 8 8Survey of existing environment 8 6 10 8 8Destruction of animal habitat and migration routes 8 5 9.5 7 7.5Topsoil preservation and reuse 8 4.5 10 7 7.5Ecological functions of drainage corridor 8 5 9 7 7.5Environmental monitoring measures after project completion 8 5 9.5 7 7.5

Landscaping 8 5 10 8 8Diversified and multilevel landscaping 8 5 10 7 7.5Vegetation coverage 8 5.5 10 8 8Carbon sequestration 7 4 9 7 7Endemic and bird- and butterfly-attracting plants 7 4 9 7 7Restoration of possible vegetation 8 5 9 7 7.5

Materials 7 5 9 7 7Use of recycled building materials 7 5 10 7.5 7.25Use of environmentally-friendly materials 7.5 5.5 9 7 7.25Application of durable materials 6 5 9.5 7 6.5Measures and equipment that are easy to maintain and manage 6 5 9 7 6.5

Waste 7 4.5 9 7 7reduction

Use of a road structure minimizing disturbance to the original 8.5 5.5 10 7 7.75ground and scenerySelection of automated working methods 7 4 8 7 7Pollution control during the construction process 7 5 9 7 7Minimization of excavation and earthmoving 8 6 9.5 7 7.5

Water 7 4 9 7 7conservation

Use of highly water-permeable side slope shapes 8 5.5 10 8 8Water-permeable pavement design 8 6 10 7.5 7.75Water storage infiltration design 7 4 10 7.5 7.25Direct infiltration design 7 4 9 6 6.5

Energy 6 3 8 5 5.5conservation

Effect of road grade on vehicle energy consumption 7 4 9 6 6.5Use of energy conservation facilities 7 4 9 6 6.5Use of natural energy or reuse of waste heat 7 4 9 6 6.5D

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durable materials would be of limited benefit givenTaiwan’s high-frequency maintenance model, whichis necessitated by the high traffic volume, overloading,and frequent excavation of underground pipelines. Thesubfactor of direct infiltration design is associated withroad structural safety; Taiwan’s relatively immatureconstruction technology in that category may accountfor the low importance of this item.

Among the major factors, the two items of ecol-ogy and landscaping had the highest importance. Thisreveals that the participating specialists felt that pasthighway construction projects had a negative impacton the local ecology and that highway landscapingwas inadequate. Future green highway constructionmust assign these two items first priority. Aftercompletion of the first stage, the original six majorfactors and 25 subfactors were winnowed down to fivemajor factors and 19 subfactors. We used the hierar-chical framework resulting from the selection processas the basis for determining weights during AHP analy-sis in the second stage.

IV. ASSESSMENT AND ANALYSIS OF THESURVEY AND FACTOR WEIGHTS

During the second stage of this study we usedthe Analytic Hierarchy Process (AHP) to analyze theimportance or weight of the different factors. AHP isa commonly used decision-making method first pro-posed by Saaty in 1971. AHP works by decomposinga complex problem into a simple hierarchical frame-work according to its different aspects. It renders aproblem hierarchical, quantitative, and structured (Saaty,1977). Here we used an AHP hierarchical framework,pair-wise comparison matrices, eigen values, andcharacteristic vector to calculate the weights of the

categories and factors to establish an assessment model.AHP requires that numerous specialists provide theirviews concerning the relative importance or weight ofthe factors of influence, to facilitate an understandingof the effect of each influencing factor on the generalindicator. The Group Decision analytical model is usedto compile these specialists’ views.

1. AHP Questionnaire

A total of 25 specialists participated in this stage,including five academics and twenty industryspecialists; the average number of years of senioritywas eleven. A summary of their backgrounds is givenin Table 7. The respondents were asked to performpairwise comparisons of all factors of influence withthe goal to determine the effect of each factor on greenhighway construction as a valuation indicator. Toensure that the specialists shared a standardized con-ception of the degree of influence, a nine level scalewas used (see Table 8).

A hierarchical green construction assessmentframework with five major factors and 19 subfactorswas established on the basis of the questionnaire results,a pairwise comparison matrix was then compiled,and the characteristic vector calculations performed.Wu take the influence of the major factors on the valu-ation indicator as an example. The pairwise com-parison matrix and characteristic vector values arecalculated as shown in Table 9. We find that the majorfactors have a maximum eigen value with regard toinfluence on the green construction valuation indica-tor of λmax = 5.0636.

To test the consistency at the different levels,we take the pairwise group comparison matrix as anexample. The value of order n for the group level of

Table 7 Background of the specialists participating in the second-stage AHP questionnaire

Number AverageSpecialist

Organization Position of years ofclassification

persons seniority

National Cheng Kung University, Professor, AssociateUniversity of Chinese Culture, Professor

Academic National Central University, 5

specialists National Taipei University of Technology,National Taiwan University of Science andTechnology

Sinotech Engineering Consultants Ltd., Engineer, Planner, 11Taipei Association of Hydraulic Engineer, Architect,Tingchiang Engineering Consultants Ltd., Landscape

IndustryGenesis Engineering Consultants Ltd. Designer, 20

specialistsGreen Empire Industrial Co., Ltd. EnvironmentalChangyuan Landscapes Development Ltd. Planner, General

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the major factors is 5, and it can be seen from Table10 that the random index (R.I.) is 1.12

C.I. (Consistency Index)

= (λmax – n) / (n – 1) =(5.0636 –5)/(5 –1)

= 0.0159 < 0.1,

C.R. (Consistency Ratio)

= C.I./R.I. = 0.0159/1.12 = 0.0142 < 0.1.

According to the foregoing calculations theC.I. of the group level is 0.0159 and the C.R. is0.0142. Since both of these are less than Saaty’s rec-ommended value of 0.1, consistency is ensured, andthe characteristic vector derived from the pairwisecomparison matrix calculations can be used as the

first-level weight ββT of the green construction assess-ment indicator as follows:

ββT = (0.3138, 0.1810, 0.1111, 0.1985, 0.1956).

A consistency test of the overall hierarchy mustbe performed to determine whether the relative impor-tances of the major factors and subfactors in the over-all hierarchical framework are consistent. This testentails calculating the consistency ratio of the hierar-chy (C.R.H.). C.R.H. is equivalent to the consistencyindex of the hierarchy (C.I.H.) divided by the randomindex of the hierarchy (R.I.H.). Overall consistency isacceptable if C.R.H. < 0.1, in which case the weight ofeach factor may be considered reasonable.

The consistency test of the overall hierarchy ofall factors influencing the green construction indicator

Table 8 Meaning of the degree of influence scale

Assessment RelativeDefinition Explanation Definition assessment

scale scale

1 Equally The two factors being compared Equally 1important have equivalent degrees of influence unimportant

3 Slightly more Experience and judgment lean Slightly more 1/3important slightly towards one factor unimportant

5 Rather more Experience and judgment lean Rather more 1/5important strongly towards one factor unimportant

7 Considerably Reality causes one to lean very Considerably more 1/7more important strongly towards one factor unimportant

9 Absolutely more There is sufficient evidence to assert the Absolutely more 1/9important absolute greater importance of one factor unimportant

Table 9 Pairwise comparison matrix and characteristic vector values of the major factors

CharacteristicWaste Water

Ecology Landscaping Materials Vector Valuesreduction conservation

(Normalization)

Ecology 1.0000 2.2914 2.8624 1.4318 1.3454 0.3138Landscaping 0.4364 1.0000 1.3976 1.1453 1.0972 0.1810

Materials 0.3494 0.7155 1.0000 0.4365 0.6424 0.1111Waste 0.6984 0.8731 2.2911 1.0000 0.8919 0.1985

reductionWater 0.7433 0.9114 1.5566 1.1213 1.0000 0.1956

conservationSum 3.2275 5.7914 9.1077 5.1348 4.9769 1.0000

Table 10 Random index (R.I.)

Order 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

R.I. 0.00 0.00 0.58 0.90 1.12 1.24 1.32 1.41 1.45 1.49 1.51 1.48 1.56 1.57 1.58

Source (Teng and Tseng, 1989)

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can be performed as follows:

C.I.H. = 0 + (0.3138, 0.1810, 0.1111, 0.1985,

0.1956)

0.00630.02170.00000.00100.0436

= 0.014631,

R.I.H. = 0 + (0.3138, 0.1810, 0.1111, 0.1985,

0.1956)

1.12001.12000.00000.90000.9000

= 0.846274,

C.R.H. = C.I.H./R.I.H. = 0.014631/ 0.846274

= 0.017289 < 0.1.

The results show that the consistency of theoverall hierarchy is acceptable, and that there is nomajor conflict between the specialists’ opinions. Table11 shows the various weights of factors influencinggreen highway construction as calculated above.

2. Analysis of the AHP Questionnaire

As can be seen from Table 11, analysis of themajor factor weights shows that ecology is weighted

the highest, accounting for 0.3 of the overall frame-work weight of 1.0; landscaping, waste reduction, andwater conservation have similar weights of approxi-mately 0.2; while materials has a relatively low weightof approximately 0.1. This indicates that ecology isregarded as the most important among the various aspectsof green highway construction. The recent surge inpublic awareness in ecological and conservation issues,and the active promotion of ecological constructiontechniques, has likely brought about a greater emphasison ecology in general. The respondents affirmedthe importance of ecology. Materials is weighted thelowest - only 0.1 – of all the major factors. AlthoughTaiwan has made considerable progress in the devel-opment and application of recycled materials andenvironmentally-friendly materials, the low weight-ing of this factor suggests that, while the respondentssupport the use of recycled and environmental mate-rials in principle, they are not thoroughly convincedthat the use of these materials can ease shortages ofnatural resources or lessen environment impact.

The three subfactors of destruction of animalhabitat and migration routes, topsoil preservation andreuse, and ecological functions of the drainage corridor,all part of the ecology category, are all weighted rela-tively high-- in excess of 0.07. In contrast, surveys ofexisting environment and environmental monitoringmeasures after project completion have relatively low

Table 11. Factor weights

Relative Relative AbsoluteMajor factors Sub-factor Rank

weight weight weight

Survey of existing environment 0.1790 0.0562 9Destruction of animal habitat and migration 0.2398 0.0752 3routes

Ecology 0.3138 Topsoil preservation and reuse 0.2259 0.0709 4Ecological function of drainage corridor 0.2494 0.0783 2Environmental monitoring measures after 0.1059 0.0332 15project completion

Diversified multilevel landscaping 0.3170 0.0574 7Vegetation coverage 0.1936 0.0350 14

Landscaping 0.1810 Carbon sequestration 0.1519 0.0275 19Endemic bird- and butterfly-attracting plants 0.1660 0.0300 18Restoration of possible vegetation 0.1715 0.0310 16

Use of recycled building materials 0.5627 0.0625 6Materials 0.1111

Use of environmentally-friendly materials 0.4373 0.0486 12

Use of a road structure that minimizes disturbance 0.1548 0.0307 17to the existing ground and scenery

Waste0.1985 Selection of automated working methods 0.2838 0.0563 8

reductionPollution control during the construction process 0.2191 0.0435 13Minimization of excavation and earthmoving 0.3424 0.0680 5

Use of highly water-permeable side slope shapes 0.4748 0.0929 1Water

0.1956 Water-permeable pavement design 0.2734 0.0535 10conservation

Water storage infiltration design 0.2518 0.0493 11

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weights, 0.0562 and 0.0332, respectively. This indi-cates that ecological protection during the construc-tion stage is the most important consideration in greenhighway construction, followed by pre-constructionsurveys, and then by monitoring after project completion.

Of subfactors in the landscaping category, di-versified and multilevel landscaping has the highestweight of 0.0574, followed by vegetation coveragewith a weight of 0.035, then by the two items of en-demic bird- and butterfly-attracting plants, and res-toration of possible vegetation, with weights of roughly0.03, and finally, by carbon sequestration, with aweighting of 0.0275. This shows that the part of land-scaping considered most important during green highwayconstruction is diversified multilevel landscaping, whichcan improve both ecological functioning and the scenery.While vegetation coverage is also considered relativelyimportant, the low weight of carbon sequestration maybe due to the complexity of the calculations neededto determine the value of this factor.

Of the two subfactors in the materials category,the use of recycled building materials has the highestweight of 0.0625, followed by the use of environmen-tally-friendly materials, with a weight of 0.0486. Thisresult is consistent with the widespread acceptance ofthe validity of recycling in recent years. However al-though the Green Mark system has been in use for sev-eral years in Taiwan, environmentally-friendly productsare not normally utilized during road construction.

Among the subfactors in the category of wastereduction, minimization of excavation is weighted thehighest, at 0.068, probably connected with the factthat highway construction projects must commonlybalance excavation and backfilling, and that spoiltreatment problems have recently received attentionin Taiwan. Selection of automated working methodshas the next highest weight of 0.0563, followed bypollution control during the construction process witha weight of 0.0435. The use of a road structure thatminimizes disturbance to the original ground andscenery has the lowest weight of 0.0307, which sug-gests that waste reduction during the constructionstage is most important, and that waste reduction dur-ing the design stage is secondary.

Among the subfactors in the water conservationcategory, the use of highly water-permeable side slopeshapes is weighted the highest at 0.0929, the highestweight of all 19 subfactors. This is probably derivedfrom the widespread dislike of the shotcrete methodof slope protection, which has been used extensivelyin highway projects, and has severely harmed the ecologyand beauty of the landscape. Next is water-perme-able pavement design, with a weight of 0.0535, andwater storage infiltration design, with a weight 0.0493.The latter two factors show that in recent highwaydesign more emphasis is being placed on water-per-meable pavement and the use of water infiltrationfacilities.

Table 12 Scoring system for the green highway assessment framework

ScoresMajor Relative Scores of

of major Sub-factorsfactors weight sub-factors

factors

Ecology 31 Survey of existing environment 0.0562 6Destruction of animal habitat and migration routes 0.0783 8Topsoil preservation and reuse 0.0752 7Ecological functions of drainage corridor 0.0709 7Environmental monitoring measures after project completion 0.0332 3

Landscaping 19 Diversified multilevel landscaping 0.0574 6Vegetation coverage 0.0350 4Carbon sequestration 0.0275 3Endemic bird- and butterfly-attracting plants 0.0300 3Restoration of possible vegetation 0.0310 3

Materials 11 Use of recycled building materials 0.0625 6Use of environmentally-friendly materials 0.0486 5

Waste 20 Use of a road structure minimizing disturbance to the original 0.0307 3reduction ground and scenery

Selection of automated working methods 0.0563 6Pollution control during the construction process 0.0435 4Minimization of excavation and earthmoving 0.0680 7

Water 19 Use of highly water-permeable side slope shapes 0.0929 9conservation Water-permeable pavement design 0.0535 5

Water storage infiltration design 0.0493 5

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V. ESTABLISHMENT OF AN ASSESSMENTFRAMEWORK AND RECOMMENDED

ASSESSMENT APPROACHES FORSPECIFIC INDICATORS

After establishing weights for the assessmentfactors, the resulting assessment framework is usedto assess the various aspects in the construction ofhighway projects, to determine whether they meet thestandards of green highway construction. We con-vert the weight analysis in the foregoing section intoa usable assessment framework designed to yield anoverall indicator specifying the actual level of sus-tainable development.

By rounding the absolute weights in percentagesfor each assessment item derived from the second-stageAHP questionnaire, we can obtain scores for each as-sessment item. The sum of the scores of subfactorsunder each major factor must be the total score forthat category, and the sum of the scores for all catego-ries must total 100 points.

Take the major factor of ecology as an example.We see that survey of existing environment has anabsolute weight of 0.0562, which is equivalent to apercentage score of 6 points after rounding. The othersubfactors in the ecology category have scores of 3points, 7 points, 7 points, and 8 points, giving thiscategory a total score of 31 points. The same methodyields scores of 19 points for landscaping, 11 pointsfor materials, 20 points for waste reduction, and 19points for water conservation (see Table12).

This appraisal framework can be used to gradedifferent highway construction projects. For instancea project can be rated based on the score as Silver,Gold, or Platinum. However, future study is neededto establish the grades and their respective score ranges.

VI. CONCLUSIONS AND SUGGESTIONS

1. Conclusions

In this study we focus on the relatively broad rangeof environmental impacts of freeways and expressways,explore the impact of the construction of highwayprojects on various aspects of the environment, andestablish an assessment model to determine whetherthe construction of highway projects complies with theprinciple of sustainable development. The results ob-tained are summarized below.(i) We determined six major green highway con-

struction assessment categories: i.e., ecology,landscaping, materials, waste reduction, waterconservation, and energy conservation, plus 25assessment items, through a review of the literature.The fuzzy Delphi method and a questionnaire surveyof specialists were used to select assessment factors.

Of the assessment factors, energy conservation hadthe lowest relative importance. Since energy con-servation fell below the threshold, it was eliminated,leaving five major aspects or categories and 19assessment items after selection.

(ii) The AHP method was used to determine the weightsexpressing the relative importance of individualfactors. The results of a specialist questionnairerevealed that, of the five major factors of ecology,landscaping, materials, waste reduction, and waterconservation, ecology had the highest weight(approximately 0.3), landscaping, waste reduction,and water conservation had similar weights ofroughly 0.2, while materials was least in impor-tance with a weight of approximately 0.1. Thisindicates that the impact of construction of highwayprojects on the ecology is considered a relativelyimportant issue.

(iii) Analysis of the absolute weight of varioussubfactors indicates that:(1) Ecological protection during the construction

stage is considered the most important eco-logical aspect. A pre-construction environ-mental survey is considered less important,and environmental monitoring after projectcompletion is considered still less important.

(2) Diversified multilevel landscaping, whichcan improve both ecological functions andscenic beauty, is considered the most impor-tant of the landscaping aspects.

(3) Although the concept of recycling is widelyconsidered the most important in the materi-als category, the application of user-friendlyproducts in highway construction of highwayhas not yet gotten underway.

(4) Waste reduction during the construction stageis considered most important in the waste re-duction category, and waste reduction dur-ing the design stage is considered secondary.

(5) Among the subfactors under water con-servation, the use of highly water-permeableside slope shapes has the highest weight of0.0929, the highest weight of all 19 subfactors.This may be because of the widespread dis-like of shotcrete slope protection, the methodmost extensively used in highway construction,which has severely harmed the ecology andthe scenic landscape. Recent highway de-sign work has started placing more empha-sis on the water-permeability of the pavementand the use of water infiltration facilities.

(iv) In this study we converted the weights of eachindicator into point scores and used them to es-tablish an assessment framework. This appraisalframework can be used to grade different high-way construction projects based on their scores.

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For instances, a project could be rated as Silver,Gold, or Platinum depending on the score.

2. Suggestions for Future Research

(i) Here we established a preliminary green high-way construction assessment framework but in-dividual indicator items, and the establishmentof assessment and scoring methods for individualitems can be a subject of future research.

(ii) Case study can be conducted in the future to fur-ther validate the developed assessment systemand to demonstrate its application to a highwayconstruction.

(iii) Further study is needed to establish the gradesof the green highway rating framework and theirrespective score ranges.

(iv) In this study we primarily focused on varioustechnical indicators, rather than difficult-to-as-sess human and social factors such as the impactof the scenery and driving comfort. These ne-glected factors can be explored in future researchso as to enhance the integrity of the green high-way construction assessment framework.

(v) We suggest that subsequent research focus on ex-tending the green construction concept to urban roadsystems and other types of construction projects.

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Chang, H., Lin, H. D., and Chen, B. C., 2000, “AComparative Study of Worldwide Technology forDesigning Green Buildings,” Research Report ofArchitecture and Building Research Institute,Ministry of Interior, R.O.C.

Chen, S. T., Chou, D. C., and Yu, B. J., 2001, “GreenConstruction Engineering Projects – A Study ofPromoting the Evaluation System and Indicatorsof Green Construction Engineering,” ResearchReport of the Public Construction Commission,Executive Yuan, R.O.C.

Chiu, M. Y., 2002, “A Study of The Application ofEcological Engineering Methods on the NationalHighway Construction,” Master Thesis, Gradu-ate Institute of Horticulture, National TaiwanUniversity, Taipei, Taiwan, R.O.C.

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Hsu, T. H., 1998, “Fuzzy Delphi Analytic HierarchyProcess (FDAHP) ,” Journal of The Chinese FuzzySystem, Vol. 4, No. 1, pp. 59-72.

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Teng, C. Y., and Tseng, K. H., 1989, “Features andApplication of the Analytic Hierarchy Process(AHP) - I, II,” Journal of the Chinese Statistics,Vol. 5, No. 27, pp. 5-22, Vol. 7, No. 27, pp. 1-15.

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Manuscript Received: May 01, 2006Revision Received: Apr. 01, 2008

and Accepted: Apr. 14, 2008

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development of an assessment framework for green highway construction

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