Sustainability assessment of road networks: A new perspective based on service ability and landscape connectivity
Introduction
In general, the prosperity of a city benefits from establishment of transport networks, but their irrational development may pose an obstacle to city sustainability. As defined by the Organization for Economic Co-operation and Development (OECD), Sustainable transport is “transportation that does not endanger public health or ecosystems and meets the needs for access” (Institution of Engineers, A, 1999). Clearly, good transportation is of a significant responsibility to keep the sustainability of economy, society and environment. However, with expanding construction, many environmental problems have appeared, such as land occupancy, noise pollution and air pollution (Lera-López, Sánchez, Faulin, & Cacciolatti, 2014; Pouresmaeili, Aghayan, & Taghizadeh, 2018). There is a strong governmental desire for a comprehensive sustainability assessment of transportation systems, though this task has proved difficult (Böhringer & Jochem, 2007).
To achieve the sustainability assessment, a lot of research has already been carried out (Finnveden & Åkerman, 2014; Salling & Pryn, 2015). And the main method is to propose an assessment system. Most researchers have the opinions that it is necessary to have a macroscopic view of the entire decision-making process in order to assess sustainability in an area of transport by using the indicators. In other words, the indicators may be considered together rather than viewed in isolation (Ortega, Otero, & Mancebo, 2014). From the definition of sustainable transport, it is clear that the indicators are classified into two aspects: the ability to serve like accessibility to facilities or public transport, and the influence of transport such as land consumption for transport (Reisi, Aye, Rajabifard, & Ngo, 2014; Rosa, Takatori, Shimizu, & Privitera, 2017). An assessment system is especially complex to build for different purposes. Currently, there is an on-going debate about the system. One viewpoint holds that however complex a system is, its establishment is subjective and not reliable (Cherchye, Lovell, Moesen, & Puyenbroeck, 2005). Even though, more researchers believe the assessment system is still an alternative tool for measuring sustainability of transport system, and this approach has been broadly explored (Shiau & Liu, 2013). In the process, characteristic indicators are differently selected to reflect one or more scenarios of sustainable transport (Toth-Szabo & Várhelyi, 2012). In addition, most of the assessment systems have been connected with transport sustainability at national level, and it is insufficient in creating the indicators for evaluating transport sustainability at local level (Shiau & Liu, 2013).
As reported worldwide, there is a visible trend that the expanded environmental and social considerations have been involved in the establishment of road networks, instead of the traditional personal mobility included in this trend since 1990s (Coppola & Papa, 2013; Gulhan, Ceylan, Özuysal, & Ceylan, 2013). According to this theory, this paper chooses the indicator “service ability”, which is calculated by the service scope of road networks to assess the ability of road networks to meet access needs. Service scope has been defined as the radiation range of each road. In the service scope, public roads would fully and conveniently “meet the needs for access”. Another essential core element in the evaluation of service ability is the service object. The main reason each road was built is generally known, such as for transportation of mining resources or for convenience to agriculture. To make the assessment specific, the service object should be taken into account.
Besides, the interdependent link of these served “sources” also determines the operational efficiency and radioactive effect of the transport network, which further produces a substantial intervention on local natural and socio-economic environments. In general, connectivity has been selected as one available indicator, which is a parameter of landscape features that measures the process of a landscape feature linked to others (Merriam & Merriam, 1984) and reflects the continuity in space of corridors (Forman, 1990). In the process, this indicator is employed to characterize the ability of some landscape element(s) to facilitate or hinder the movement (Fahrig, 1993; Minor & Urban et al., 2008). Environmentally and sustainably, the key to maintaining biodiversity is the dispersal ability of organisms across changing landscapes (Fahrig, 2007), and enhanced landscape connectivity is beneficial for promoting biodiversity and ecosystem integrity (Liu et al., 2014). There is, hereby, the landscape connectivity can show some impacts from the roads construction (Ferreira et al., 2016; Gulhan et al., 2013; Igondova et al., 2016), and the road becomes one main element responsible for the loss of connectivity (Gurrutxaga et al., 2011). Therefore, the connectivity is regarded as a highly effective bridge for various environments (Ng et al., 2013). With the expanded connotation of “connectivity”, socio-economic communication has been a critical consideration in construction of road networks (Ahmed et al., 2008).
The effect of expansion of road networks on the comprehensive function has drawn attentions throughout the world, and these studies have concentrated on the impact of roads on land use change (Wu, Lin, Chiang, & Huang, 2014) and habitat fragmentation (Fu, Liu, Degloria, Dong, & Beazley, 2010; Liu et al., 2014; Tournant, Afonso, Roué, Giraudoux, & Foltête, 2013), which, if the road transport is always kept in dynamic expansion, are the recurring causes and consequences of city development and redevelopment, but the only unchanged thing is the function of road transports. Clearly, the sustainable transportation is characterized by two key points of not endangering ecosystem services as well as meeting the needs for access which answers what and why it serves (Castillo & Pitfield, 2010). Around this core, this study attempts to employ two major indicators of service ability and landscape connectivity to present the sustainability of road transports in a Chinese mining city, which covers a mix of agriculture, industry, forest, nature reserve, etc., and whose road transports are of a variety of service functions. Therefore, the objectives of this study are (1) to estimate the service ability of road. (2) to assess the influence on ecological environment by calculating the different landscape connectivity with and without roads. (3) to achieve the sustainability assessment. Achieving these objectives will provide the government and policy makers with useful information for future land planning and nature conservation, such as measurements of the ecological interference of road construction, which can help in the decision of whether to build.
Section snippets
Description of study area
Wu’an is used as a case study to propose a system for assessing the development of the road network. It is in Hebei province, China, which lies at the eastern foot of the Taihang Mountains, located at 113°45′∼114°22′E, 36°28′∼37°01′N (Fig. 1). Wu’an has a population of about 720,000 people and covers a surface area of 1819 km2. The whole city is surrounded by mountains and possesses rich mineral resources. Due to the special location and resources, agriculture and the mining industry both
Service ability of road networks
There is a significant widening gap in the service ability of road networks compared with China's average value of 0.201 km/km2 in 2005 (Jilai, Haifeng, & Xinping, 2006). The density of road networks in Agricultural zone 1 is greater than that in the Mining zone, while the densities in the Comprehensive zone, Forest zone 2 and Agricultural zone 2 are nearly equal. Forest zone 1 has the lowest road network density, which was nearly one third that of Agricultural zone 1 (Table 2).
Density is an
Main achievements
Generally, a mass of indicators are included to assess transport systems (Reisi et al., 2014). However, this study selects two indicators, the service ability and the interference with landscape connectivity with a focus on local-level transport, and is still significant. The study area is classified into different functional zones, and each has its own requirements for roads. The evaluation of indicators is also different from those of other sustainability studies, whose values were directly
Acknowledgements
This article is supported by National Natural Science Foundation of China (Grant No: 41571507, 41101531, 41401622) and Beijing Higher Education Young Elite Teacher Project (No. YETP0639). Also, authors gratefully acknowledge the colleagues and friends in Land Resources Bureau of Wu’an for offering the basic data and the relevant information.
References (47)
- et al.
Urban transportation and equity: A case study of beijing and karachi
Transportation Research Part A
(2008) - et al.
Measuring the immeasurable — A survey of sustainability indices
Ecological Economics
(2007) - et al.
Elastic - A methodological framework for identifying and selecting sustainable transport indicators
Transportation Research Part D-Transport and Environment
(2010) - et al.
Accessibility planning tools for sustainable and integrated land use/transport (lut) development: An application to rome
Procedia - Social and Behavioral Sciences
(2013) - et al.
Evaluation of the steel slag incorporation as coarse aggregate for road construction: Technical requirements and environmental impact assessment
Journal of Cleaner Production
(2016) - et al.
Not planning a sustainable transport system
Environmental Impact Assessment Review
(2014) - et al.
Characterizing the “fragmentation–barrier” effect of road networks on landscape connectivity: A case study in xishuangbanna, southwest china
Landscape and Urban Planning
(2010) - et al.
Impact of utility-based accessibility measures on urban public transportation planning: A case study of Denizli, Turkey
Cities
(2013) - et al.
Key connectors in protected forest area networks and the impact of highways: A transnational case study from the cantabrian range to the western alps (sw europe)
Landscape and Urban Planning
(2011) - et al.
The ecological impact assessment of a proposed road development (the slovak approach)
Environmental Impact Assessment Review
(2016)