Internationales Verkehrswesen (66) 1 | 2014 44 Green Roads Further requirements for sustainability evaluation of highway projects - Comparison and analysis of existing rating systems for infrastructure projects Sustainability rating systems are gaining more and more importance for public authorities, contractors and clients. Established approaches for sustainability evaluation of infrastructure projects, as ENVISION, CEEQUAL or the IS-Rating System, ofer numerous diferent criteria in order to evaluate environmental, economic and social performance. Due to a missing international standardisation, rating systems vary in structure, applicability and range of criteria. By using the example of assessing highway projects, evaluation limits caused by general criteria or neglecting economic, technical and processrelated aspects become obvious. Hence, existing rating systems have to be extended in-order to ensure a holistic sustainability assessment. The Authors: Sascha Hofmann, Ivan Čadež T he transportation sector represents an important factor for global economy; it is responsible for 22 % of global energy consumption, 25 % of fossil use and 30 % of global air pollution along with greenhouse gas emissions. It also accounts for approximately 10 % of the world´s gross domestic product (GDP) [1]. Hence, a sustainable development is becoming more and more important for the construction industry, design teams, institutions and its clients. In order to determine a projects´ sustainability performance and to reduce its environmental, social and economic impacts, it is necessary to identify and measure appropriate criteria. To meet this demand, sustainability rating systems are widely-used tools during planning and design phase of projects [2]. Sustainability rating systems are based on the Triple Bottom Line concept. This approach considers environmental, social and economic aspects the three dimensions of sustainability. The concepts main aim is protecttion of natural resources. In recent years the Triple Bottom Line concept has served as a common ground for numerous sustainability standards and rating systems in Foto: Rainer Sturm/ pixelio.de INFRASTRUKTUR Wissenschaft Internationales Verkehrswesen (66) 1 | 2014 45 Wissenschaft INFRASTRUKTUR general as well as for the construction industry in particular. In accordance with the demand of a holistic sustainability determination, rating systems have to provide a wide range of speciic evaluation criteria for the three sustainability dimensions [3], [4]. Sustainability assessment methods have recently occurred primarily in vertical construction (buildings). Since 2005 several assessment methods for horizontal and public infrastructure projects have been developed or are currently under development [2], [4], [5]. Though, development of rating systems for horizontal and vertical projects is proceeding almost independently from each other. Sustainability rating systems for infrastructure projects Currently infrastructure projects’ sustainability is widely rated by three internationally established assessment approaches ENVISION (USA), CEEQUAL (GB) and the IS- Rating Scheme (Australia). All approaches difer in terms of structure, applicability and evaluation criteria. An overview of the systems applicability and their criteria framework is presented in table 1. ENVISION is a web-based sustainability project assessment and guidance tool operated by the Institute for Sustainable Infrastructure (ISI) in the USA. The ENVI- SION rating system is a single rating approach which includes design, planning, construction and operation elements for evaluation. The approach is assessable to six groups of infrastructure construction types: energy generation, water storage and treatment, waste management, transport, landscape and information systems. Thereby ENVISION is able to rate a total of 37 types of projects. It serves a total number of 60 rating criteria within ive categories for a projects life cycle [6], [7], [2]. The Civil Engineering Environmental Quality and Assessment Scheme (CEEQUAL) is a UK-based sustainability rating system for civil engineering, infrastructure, landscaping and public realm projects. The assessment scheme was initiated for horizontal projects as an equivalent to the BREEAM rating method for vertical projects. CEEQUAL is not limited in its use and is applicable to all kind of civil engineering projects. It contains a framework of approximately 180 questions assigned in 12 categories relating to aspects of environmental and social concern. As a key diference to other rating systems CEEQUAL is matched to each project being assessed by scoping out non-relevant questions which leads to varying evaluation criteria frameworks. [5], [8], [9]. Developed and launched by the Infrastructure Sustainability Council of Australia (ISCA) the IS-Rating Scheme is a voluntary sustainability assessment method for the infrastructure market. It includes 15 rating criteria distributed into six categories. The rating scheme is comprised of a technical manual, a rating tool scorecard and a material calculator. Applicants have to follow a fourstep assessment process: project registration, assessment, veriication and certiication. The IS-Rating system supports diferent rating phases (design, construction and operation phase). The scheme can be used for ten diferent construction types distributed into four groups. It is applicable only to selected infrastructure types as transport, water, energy and communication and focuses mainly on transport infrastructure projects as airports, railways, roads, ports and cycleways [10]. The three analyzed international rating methodologies are applicable for planning, design, construction and operation phase and cover diferent numbers of rating criteria and categories. Though, all approaches cover almost the same criteria framework. ENVISION difers from CEEQUAL only by neglecting issues of transportation. The IS-Rating Scheme and CEEQUAL are almost equal while their rating criteria are only distributed into varying numbers of categories. Currently none of the analyzed approaches provides economic rating criteria in order to evaluate economic sustainability perfor- Groups of assesable infrastructure types Rateable construction types Rating categories Rating criteria ENVISION 6 • Energy Generation • Water Storage & Treatment • Waste Management • Transport • Landscape • Information systems 37 5 • Quality of Life • Leadership • Resource Allocation • Natural World • Climate and Risk 60 CEEQUAL ∞ • Unlimited; all kind of horizontal civil engineering constructions ∞ 12 • Project Environmental Management • Ecology and Biodiversity • Use of Materials • Water • Energy • Waste • Land use • Landscape • Archaeology and Cultural Heritage • Transport • Nuisance to Neighbours • Community Relations Approx. 180 IS-Rating System 4 • Transport infrastructure with focus on: airports, railways, roads, ports and cycleways • Water • Energy • Communication 10 6 • Management & Governance • Using Resources • Emission, Pollution & Waste • Ecology • People & Places • Innovation 15 Table 1: System applicability and criteria framework of infrastructure rating systems Internationales Verkehrswesen (66) 1 | 2014 46 INFRASTRUKTUR Wissenschaft mance of a project. Criteria frameworks of the three rating systems are related to mainly environmental and social aspects of a project which is contrary to the demands of the Triple Bottom Line concept. Evaluation limits of existing rating systems concerning highway assessments Existing rating systems for infrastructure projects display three major weaknesses. By using the example of highway assessments the following evaluation limits can be identiied: 1. Conlict of general criteria framework 2. Disagree to the Triple Bottom Line concept 3. Neglect of technical and process-related aspects Assessing various types of infrastructure projects requires a general criteria framework. However, general criteria prevent a detailed evaluation of speciic requirements and functions for diferent construction types. A projects’ main function (e. g. transportation, water storage) is the most important indicator for its sustainability requirements. Depending of a projects´ function environmental, economic and social aspects vary in importance and weight. For example, an airport causes higher environmental and social impacts in terms of land use or emissions compared to a wind power plant. This entails varying sustainability standards for assessing infrastructure projects. In addition it is necessary to consider the relevance of a project for its user and community. Compared to private operated projects publicly available infrastructure projects difer in their sustainability requirements related to e.g. safety and health issues. Hence, it becomes apparent that a general criteria framework is not suicient for speciic sustainability ratings and is not able to meet speciic technical characteristics of highways [11], [12]. Compliance with the Triple Bottom Line is basic prerequisite of sustainability assessments. Current European engineering standards as ISO/ TS 21929-1: 2006, ISO 15392: 2008 and EN 15643-1: 2010 provide general information and core indicators for sustainability rating systems and are applicable to buildings and other construction works. Existing standards are completed by the ISO/ TS 21929-2 for infrastructure constructions which are currently under development. A homogeneous international standardization for sustainability ratings has not been inalized yet [13], [14], [15]. Existing rating systems for infrastructure projects do not meet the needs of a holistic environmental, economic and social evaluation. Criteria frameworks of CEEQUAL, ENVISION and the IS-Rating Scheme serve mainly environmental and social aspects. Particularly with regard to economic criteria (e. g. life cycle costs, economic value and stability) these approaches neglect important aspects of sustainability. Thus, established rating schemes have to be extended for holistic sustainability evaluations of transport infrastructure projects in general and highway projects in particular. Transport infrastructure projects present signiicant possible savings in sustainability since they are large in scope, typically long in duration and serve numerous complex technical and process-related challenges. Construction phase of highways is afected by reiterating processes and a high output of emissions. Main function of the bearing structure is to transfer accelerating, breaking and centrifugal forces into ground. Furthermore the covering has to absorb atmospheric inluences as frost, rain or incident solar radiation. Planning, design, construction and operation processes have to be adapted to these speciic requirements. This afects the choice of construction materials as well as its assembling methods. During operation phase maintenance of road safety, trafic low and quality of traic are of prime importance [15]. Use of resources and materials as well as quality and safety issues are speciic evaluation criteria for highway projects [2], [11]. But especially construction processes and technical facilities afect economic, environmental and social aspects and therefore also a projects´ sustainability. Project preparation, construction methods, technical standard of pavements or design of subgrade bearing structure have to be considered. In addition capacity reserves for future lane enlargements or cleaning, recycling and maintenance concepts are important criteria which cannot be allocated to one of the three existing sustainability dimensions. Hence, technical and processrelated aspects are contributing factors for a projects´ sustainability performance and should be implemented into future assessments [15], [11]. Review of the three major sustainability rating systems reveals that a general sustainability approach is not appropriate to evaluate speciic sustainability performance of a project as technical, functional, process-related issues as well as user-/ operator-speciic aspects remain disregarded. Though, it is obvious that environmental, social and economic impacts of a project are inluenced by the technical standard of facilities as well as by their processes in design, construction and operation phase [11]. To what extent sustainability is achieved remains uncertain since there is no consensus regarding system applicability, base design, assessment process, AUF EINEN BLICK Nachhaltigkeit hat sich zu einem wichtigen Kernthema auf höchster Managementebene entwickelt. Nachhaltigkeitszertiikate gewinnen als Entscheidungskriterium für öfentliche Auftraggeber, Investoren und Nutzer immer mehr an Bedeutung. Dieser Trend ist auch bei Infrastrukturprojekten erkennbar. ENVISION, CEEQUAL oder das IS-Rating System stellen erste internationale Ansätze zur Bestimmung von ökologischen, ökonomischen und soziokulturellen Aspekten für die Bewertung der Nachhaltigkeit von Infrastrukturprojekten dar. Aufgrund einer bislang fehlenden einheitlichen Normung unterscheiden sich die Bewertungsansätze hinsichtlich der Struktur, der Bewertungsmethodik, des Anwendungsbereichs und der Bewertungskriterien voneinander. Am Beispiel der Verkehrsinfrastruktur, speziell den Autobahnen, werden die Bewertungsgrenzen existierender Systeme deutlich. Insbesondere hinsichtlich der allgemeinen Bewertungskriterien sowie der fehlenden Berücksichtigung ökonomischer Aspekte werden Optimierungspotenziale deutlich. Für eine ganzheitliche Betrachtung der Nachhaltigkeit ist zudem eine Berücksichtigung von technischen und prozessualen Kriterien erforderlich. Internationales Verkehrswesen (66) 1 | 2014 47 Wissenschaft Infrastruktur validation, criteria framework or weighting of criteria. This fact is owed by a missing international standardization for sustainability assessment and detracts the comparability of established systems [2], [4], [15]. Hence, existing rating systems have to be extended in terms of structural standardization as well as in terms of implementation of processes and technical aspects. Conclusion Comparison and analysis of established sustainability rating systems reveal that recent approaches are not suficient for holistic assessments of infrastructure projects in general as well as transport infrastructure projects in particular. Due to missing international standards sustainability certiication processes are varying in their methodologies and their applicability concerning diferent types of infrastructure projects. By using the example of highway projects three major improvement opportunities have been identiied: 1. Speciication of general criteria framework 2. Adaption to the Triple Bottom Line concept by considering economic aspects 3. Implementing technical and process-related aspects By achieving the identiied improvement opportunities comparability, signiicance and acceptance of sustainability evaluations can be increased. This leads to the conclusion that an extended sustainability rating approach is required. First suggestions for an improved sustainability rating system for transport infrastructure projects have been made in [11] and [12]. ■ REFERENCES  [1] Eisenman, A. A. P. (2012), Sustainable Streets and Highways: An Analysis of Green Roads Rating Systems, School of Civil & Environmental Engineering, Georgia Institute of Technology, Georgia, USA, 2012.  [2] Clevenger, C. M.; Ozbek, M. E.; Simpson, S. 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Faculty of Architecture and Civil Engineering, Chair-of Real Estate and Construction Management, Technical University of Dortmund, Germany ivan.cadez@tu-dortmund.de Eberhard Buhl, M.A. Redaktionsleitung Telefon (040) 23714-223 Telefax (089) 889518-75 eberhard.buhl@dvvmedia.com IHR KURZER DR AHT ZUR REDAKTION © freni/ pixelio.de