According to the results in the previous section, we noted that most of the sample provinces in this study have been making good progress in improving LSTD. In fact, majority of them are located in the quadrant I (H-H). It is considered that the progress is the results of taking SDGs as the crucial guidance in developing transportation systems across all provinces. In other words, we believe that SDGs are crucial guidance for achieving sustainable transportation development. Those provinces which pursue continuously SDGs have generally performed better LSTD. For instance, Sichuan province have been developing and upgrading their public transport systems in recent years. These transportation development progress not only provide more convenient travel options for publics, but they also offer more jobs, especially in the areas of rail transit, bus services. These policy and measures and action are closely associated with SDG 8 (Decent Work and Economic Growth) (Anwar et al., 2021). According to the study by S. Zhang et al. (2021), Sichuan Province's carbon mitigation strategies, crucial for achieving Sustainable Development Goal 3, significantly reduced PM2.5 concentrations by 2035 and yielded health co-benefits worth 23 billion USD. In Jiangsu, a strong economic province in eastern China, improvements in the transportation system have significantly enhanced regional connectivity and the efficiency of economic activities, aligning with SDG 9 (Industry, Innovation, and Infrastructure). Expanded and optimized transport networks have facilitated local business activities, boosting economic growth, in line with SDG 8. In terms of environmental impact, provinces like Zhejiang and Guangdong have achieved significant environmental benefits by promoting clean energy and improving transportation infrastructure (Ju, 2023; Wang et al., 2022). Zhejiang, in particular, has focused on incorporating electric and hybrid vehicles into its transportation system, not only reducing dependency on fossil fuels but also significantly lowering greenhouse gas emissions from transportation, consistent with SDG 13 (Climate Action). Simultaneously, Zhejiang's urban planning has increased green spaces and public transport, effectively improved air quality and aligning with SDG 11 (Sustainable Cities and Communities). The efforts of these provinces in advancing sustainable transportation not only demonstrate their commitment to individual SDG targets but also showcase the synergistic and reinforcing interplay among multiple SDGs in the process of achieving sustainable transportation. A holistic consideration of multiple SDGs allows for comprehensive progress in transport efficiency, environmental protection, social welfare, and economic development.
During the survey period (2015–2020), most provinces demonstrated a relatively stable trajectory and significant regional clustering in terms of the performance of LSTD, evidenced with their unchanged quadrant positions. Specifically, coastal provinces of Anhui, Hebei, Henan, Hubei, Hunan, Jiangsu, Shandong, and Zhejiang have positioned consistently in the first quadrant for the whole survey period, highlighting that their transportation development progress are comprehensive, balanced and in line with the required of SDGs. This performance outcome is attributed to the substantial investments in transportation infrastructure, which is allowed by their strong economic strength (Magazzino & Mele, 2021). Hepburn et al. (2021) pointed out these coastal provinces have better urban planning, more investments in clean energy transportation, and improvements in traffic safety and efficiency. They have not only set examples for regional cooperation but also established high standards for LSTD.
In referring to the second quadrant provinces, Including Guizhou, Hainan, Jiangxi, Shanxi, Shaanxi, Shanghai, Tianjin, and Chongqing, although their performance in LSTD is not high, they have the potential to improve their development through cooperations with their good-performed neighbors. It is considered that effective regional collaboration is a key strategy to making progress in the LSTD. Vulevic et al. (2020) opined that regional cooperation can drive sustainable transportation, evidenced by analyzing accessibility challenges and innovations in the Alto Alentejo (Portugal) - Badajoz (Spain) cross-border region, revealing crucial indicators and strategic investment needs for long-term sustainable transit solutions.
Qinghai, Xinjiang, and Inner Mongolia are third-quadrant provinces consistently. They locate in western China and limited by remote geography and scarce resources. Previous studies suggest that these western provinces cannot attract capital and labor (Gupta et al., 2021; Ling et al., 2022; Warchold et al., 2022).
The only two provinces, namely Guangdong and Sichuan, have reasonably good performance in LSTD themselves but are neighbored with poor performers. This situation highlights the unevenness of regional development and underscores the urgent need to promote LSTD. Several factors contribute to this disparity. Firstly, Guangdong and Sichuan have benefited from proactive government policies that prioritize sustainable transportation initiatives, supported by substantial investments in infrastructure. Secondly, these provinces have a more robust economic foundation, enabling them to adopt advanced technologies and sustainable practices more readily. In contrast, neighboring provinces may lack such financial flexibility and governmental support. Thirdly, Guangdong and Sichuan's geographical and cultural advantages have fostered tourism and international trade, further driving the development of sustainable transportation to cater to these sectors.
The changes in quadrant positions of Beijing and Guangxi are particularly noteworthy, highlighting the dynamic evolution and strategic adjustments in China's sustainable transportation. The shift in Beijing's quadrant position from the first quadrant in 2015 to the third quadrant by 2020 primarily stems from challenges associated with urbanization, such as traffic congestion and air pollution, as well as the profound impact of the city's economic structural transformation on transportation demands and infrastructure. Moreover, policy shifts, including increased investment in public transportation and the promotion of new energy vehicles, while beneficial in the long run, may have had short-term adverse effects on Beijing's performance in sustainable transportation evaluations. This confluence of factors collectively contributed to the significant change in Beijing's sustainable transportation landscape. Conversely, Guangxi's ascension to the first quadrant by 2020 significantly marks the province's substantial progress in the field of sustainable transportation. This shift highlights Guangxi's rapid strategic advancements towards sustainable development, greatly aided by its vibrant manufacturing industry and geographical proximity to the economically dynamic region of Guangdong. Additionally, national policies supporting regional interconnectivity, such as the China-ASEAN Economic Corridor, have also played a crucial role in stimulating its growth. Guangxi's leap not only underscores the dynamic nature of sustainable transportation development but also demonstrates the immense potential of historically lower-developed regions to achieve sustainable development goals through targeted policies, regional cooperation, and learning from neighboring high-performing provinces. The cases of Beijing and Guangxi are particularly noteworthy, revealing the unique challenges that megacities face in sustainable transportation development, and the pivotal role of regional development policies in elevating the sustainable transportation levels of provinces.
In summary, to promote the Level of Sustainable Transportation Development in China, we recommend several key policy measures. Firstly, to increase the coverage and efficiency of public transport, which is also requested in SDGs. According to Wu et al. (2023), the coverage rate of public transport is still much lower them that in the developed countries. This can be achieved by expanding public transport networks, improving service quality and reliability. Secondly, to promote the use of clean energy vehicles for reducing dependence on fossil fuels and greenhouse gas emissions. It is widely appreciated that promotion for clean-energy transportation is an important strategy for achieving LSTD (Razmjoo et al., 2022). This can be achieved through introducing financial incentive measures for purchasing clean energy vehicles. Thirdly, to increase the transportation linkages between different provinces. As pointed by Bao et al. (2023), linkage different provinces is a key measure for achieving LSTD. This can be achieved by increasing urban agglomeration, which involves the strategic development of interconnected urban areas that support efficient and sustainable transportation networks, enhancing both regional connectivity and economic synergy. Furthermore, to establish a monitoring and evaluation system for ensuring sustainable transportation development. It is important to assess whether the development of transportation system is in line with SDGs. Ahad et al. (2020) suggested that measuring and evaluation are important machines for ensuring the development of transportation system towards better sustainability. This requires regular collection and analysis of transportation data, assessing the effects of policies and projects, and promoting cross-sectoral and cross-regional information sharing and coordination.