Spatial impact analysis of trans-Yangtze highway fixed links: A case study of the Yangtze River Delta, China

Abstract

As an important infrastructure connecting straits or rivers, the construction of fixed links has become an effective measure for improving traffic conditions and promoting socio-economic development in many countries and regions around the world. Thus, it has become a significant topic in the field of transport geography. Taking the Yangtze River Delta as its case area, this study proposes a spatial impact model of trans-Yangtze highway fixed links, consisting of three components: an accessibility model, modified gravity model, and traffic utilisation model, which are used to analyse, respectively, cross-Yangtze accessibility and changes to transport structure, cross-Yangtze urban interaction and changes to economic structure, and the utilisation relationship of fixed links. Making use of existing fixed links while planning and building new ones has become the basis for achieving regional integration and sub-regional cooperation in this area, the aim of which is to create the barrier-free circulation of elements. The results prove that this spatial impact model coincides with reality. The increase in the number of fixed links has significantly shortened cross-river travel time and facilitated a unification of north-south highway networks. It has also promoted the formation of a high-connection urban network along the river. Northern urban nodes have joined the southern economic circle and finally achieved north-south integration. There are complex relationships between fixed links and their hinterlands, showing obvious utilisation gaps between the links. The complete system of trans-Yangtze fixed links is comprised of several river crossing facilities and connected highways. The function of each link is related to its role in the regional highway network. From a small number of fixed links to the realisation of multiple trans-Yangtze bridges and tunnels with easy access to multiple arterial highways, a ‘many-to-many’ spatial pattern is created that ultimately leads to the evolution of regional transport and economic structures.

Introduction

Social and economic growth and the formation and evolution of spatial structures in the urban agglomeration are closely intertwined with the development of the transport network (Rodrigue et al., 2009). The construction of new infrastructure reduces the communication costs between cities and overcomes connection barriers to key elements such as labour, cargo, capital, technology, and information created by spatiotemporal distances in the region (Janelle and Beuthe, 1997; Vickerman et al., 1999). It also changes the strength and direction of interactions between cities (Jiao et al., 2017; Rong, 2002) to achieve optimisation and reorganisation of regional economic linkages and the hierarchical structure of the urban system (Knowles, 2006; Lu, 1995). Many of the world's largest urban agglomerations are located near bays or river deltas. As important components of regional transportation infrastructure, trans-strait or trans-river highway fixed links reconnect urban networks separated by straits or rivers, which serve middle- and long-distance carriage and also taking commutes between riverside urban nodes into consideration (Arliansyah et al., 2015). With the development of bridge and tunnel construction technology, fixed links have become the main form of connection between the two sides of a river or strait and an option that fits the long-term development pattern of the region. Compared with ferries, this form of traffic is faster, has higher capacity, and is less affected by hydrological and meteorological conditions (Díez-Gutiérrez and Tørset, 2019). This process has occurred in the Yangtze River Delta, where the large-scale construction of fixed links began around 2000. trans-Yangtze infrastructure has an important impact on the regional traffic network and thus promotes socio-economic development. The purpose of this paper is to study this spatial impact and reveal its role.

Existing studies show that fixed links break down the spatial barriers of rivers or straits, playing an important role in improving the quality and quantity of elements of communication between shores (Gibb, 1988) and guiding the centralisation and diffusion of elements through them. The construction of fixed links can improve regional internal and external traffic conditions, especially along rivers or close to straits. Impacts on the economic development, regional spatial structure, and industrial transfer layout of both shores are all derived from the ‘spatiotemporal compression’ benefit generated by the links (Wu et al., 2012). Most directly, inter-city highway accessibility is improved. A unified highway network decreases the traffic cost between shores and has an obvious spatial convergence effect on regional transportation organisation (Liu et al., 2019). On this basis, the structural pattern and dominant direction of the two shores' economic contact is affected (Knowles and Matthiessen, 2009).

In terms of traffic impact, convenient cross-strait or cross-river transport increases accessibility between cities on both sides, and relatively independent road transport infrastructure networks on both sides tend to be integrated (Vickerman, 1995; Zhao et al., 2017), which becomes the basis for coordinating urban spatial connection between shores (Sun et al., 2014). Wu et al. (Wu et al., 2007) and Hou and Li (Hou and Li, 2011) measured the changes to inter-city travel time in city clusters with an increasing number of fixed links, taking the Yangtze River Delta and the Pearl River Delta as examples. Meanwhile, it is believed that there are regional discrepancies in the accessibility impacts on fixed links (Bruyelle and Thomas, 1994), with riverside or less developed areas being more affected (Wu et al., 2009).

In terms of economic impact, the spatial interaction of elements on two sides of a river or strait and the influencing factors are explained and analysed by comparing the situation before and after the construction of fixed links and by forecasting the future. Gutiérrez et al. (2016) and Andersen et al. (2018) established the analysis models under the influence of trans-strait infrastructure, taking Norway as an example, explaining the population matching differences caused by changes in multiple factors. McKinnon (1994) was among the first to discuss the effects of trans-strait fixed links on time-sensitive industry sectors. Sen (2004) and Garnett (1993) analysed the impact of the English Channel Tunnel on the development of British tourism. Gao et al. (2018) and Skjött-Larsen et al. (2003) analysed the development of the logistics industry after the two ends of the strait had been connected, arguing that the completion of the projects had rendered areas around the links important logistics centres of their respective regions. Matthiessen (1993) tracked the trans-strait fixed link planning and construction processes of Scandinavian and Danish islands' connection to the European continent, which have changed the layout of the transport industry (Matthiessen, 2004). Nilsen et al. (2017) discussed the economic benefits from ex-post analysis at a firm level for trans-strait projects, suggesting that increased competition has side effects.

Numerous studies have revealed the impact of cross-strait and cross-river facilities on the spatial organisation of regional economies. Regional integration can be achieved by the gradual elimination of the economic, social and cultural separation of two sides through fixed links (Matthiessen, 2000). Such large-scale infrastructure construction connects the central cities (growth poles) of the region and reduces the costs of element exchange (Lan et al., 2016; Wang and Meng, 2004), directing their diffusion through road networks and leading to a rational configuration (Andersen et al., 2016; Meijers et al., 2012). The relationships between projects and economic growth have been considered (Sun et al., 2010). Large cities in urban agglomerations along traffic corridors with a cross-strait or cross-river advantage are likely to be major beneficiaries (Wang, 2006; Wu et al., 2015). After the construction of the English Channel Tunnel, although Kent and Calais, the cities located at the exits of the link, were the most direct beneficiaries of the connections, the biggest beneficiaries were in the metropolitan areas further from the coast, including Lille and London (Thomas and O'Donoghue, 2013). Scholars who have summarised the above spatial impact processes have proposed several influence models. Based on a study of the Fehmarn Belt Bridge connecting Denmark and Germany, Matthiessen and Worm (2011) first systematically proposed a spatial impact model for a trans-strait fixed link. The model explains the existence of a ‘core-periphery’ pattern under the influence of fixed connections. Later, Wu et al. (2017) modified the fixed link model using complete city clusters by conducting a case study of the Pearl River Delta urban agglomerations. The process and mechanism of how fixed links resolve the communication issues between cities separated by a strait have been explored. These scholars have suggested that fixed links will become new hot spots for urban expansion and will accelerate the network integration of cities on both shores. Subsequent changes in population, industry, land use, and transportation transform the spatial patterns of regional economic growth.

The Yangtze River Delta (YRD) is one of the regions with the highest level of social and economic development in China. The Yangtze River divides the region into two parts, north and south. Using existing trans-Yangtze facilities, new planning and construction to attract barrier-free circulation of elements between the north and the south has become the material guarantee for the realisation of the integrated development of urban agglomerations and the promotion of sub-regional cooperation in the YRD. For many years, there have been distinct conflicts between cross-river demands and supplies. The reason for this is that, firstly, cross-river traffic grows rapidly, and secondly, which cannot be ignored, the fixed link is an expensive project, both financially and technically. The Nanjing Yangtze River Bridge, for example, cost USD 117 million in 1968. With improved construction technology and a newly planned expressway network, fixed links have replaced ferries as the mainstream and more economically appropriate option (Taffe and Gauthier, 1973). This way of river crossing caters to the spatial organisation of YRD urban agglomerations, eliminating the historical differences in developmental levels between cities and enhancing the ability of underdeveloped areas to receive industrial transfers from developed areas (Lu and Dong, 2017). So far, nearly 20 fixed links have been put into operation. However, the impacts of relatively few have been studied from a geographic perspective.

In this paper, we construct a spatial impact model that contains multiple trans-Yangtze fixed links to analyse the impact on cross-Yangtze accessibility. The evolution of economic linkages between cities on the northern and southern coasts is also discussed, as well as the characteristics of network utilisation and fixed link interrelations, with the aim of enriching and developing theory and practice related to fixed links between two banks or across rivers. Section 2 of the article covers the analytical framework and theoretical model of trans-Yangtze fixed links. Section 3 introduces the methods, data sources, and pre-processing procedures. Section 4 presents the analysis results, and Section 5 covers the discussion. Section 6 is the conclusion.