# **1. Introduction**

The number of ongoing and proposed initiatives for transport corridors is increasing. One ambitious proposal is to revive the Grand Trunk Road from Kabul, Afghanistan, to Chittagong, Bangladesh, connecting areas that are home to a significant share of the world’s poor. An even more ambitious initiative is the Belt and Road Initiative proposed by China, which aims to improve connectivity and cooperation on a transcontinental scale through significant infrastructure investments around the Silk Road Economic Belt and the New Maritime Silk Road (World Bank 2019).

Developing large transport corridors is increasingly seen as a way to stimulate regional integration and economic growth. Countries, often with the help of the international community, invest in these corridors hoping to boost private sector investments and trade, create jobs, and improve economic welfare. However, these wider economic benefits (WEBs) go beyond the user benefits—that is, savings in vehicle operating costs and travel time—of the specific transport improvements, which are usually the focus of appraisal of transport corridors (ADB, DFID, JICA, and World Bank 2018; Laird and Venables 2017).

Interest in studying the WEBs of large transport infrastructure projects is growing (Behrens, Brown, and Lonla 2016; Redding and Turner 2015).<sup>1</sup> Attention is turning to economic benefits that go beyond trade and efficiency gains at the aggregate level, to consider benefits that reach not only large national and international economic actors (corporations and foreign traders), but also smaller and more localized ones (micro, small, and medium-size enterprises), as well as poorer people. The interest has been propelled in part by the increasing number of transport corridor initiatives justified based on their potential but uncertain WEBs.

The literature on the WEBs of corridors typically looks at a single corridor to assess impacts. However, there is much to learn from differences across projects and the resulting variation in the design and implementation of transport investment projects and the practitioners working on them. This paper aims to shed light on the link between project design and implementation and WEBs and help bridge the divide between the academic literature on WEBs and the practical project design and appraisal.

The paper assesses which design and implementation characteristics of transport corridor projects and country characteristics could help maximize the WEBs from transport corridors. To analyze this question, we collected data on transport corridor projects supported by three international development organizations: the Asian Development Bank (ADB), the Japan International Cooperation Agency (JICA), and the World Bank.

The paper contributes to two strands of the literature. One strand focuses on estimating the WEBs of large transport infrastructure, using detailed locational data. Several studies summarize the estimated impacts of transport infrastructure investments and applied estimation approaches using qualitative approaches (Berg et al. 2017; Redding and Turner 2015; Straub 2011) or quantitative methods, such as systematic reviews and meta-analyses (Melo, Graham, and Brage-Ardao 2013; Roberts et al. forthcoming). The literature estimates that, on average, the impacts of corridor investments on economic welfare and equity tend to be beneficial, although they are often detrimental for environmental quality. Roberts et al. (forthcoming) highlight that, around this positive average impact, the local impacts could vary widely depending on the

> 1 For a review of the literature, see Roberts et al. (forthcoming).

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