Quantitative measurement on urbanization development level in urban Agglomerations: A case of JJJ urban agglomeration

• A CG-GSO model is proposed to measure the urbanization development level. • The model restores the nonlinear urbanization development in urban agglomeration. • The JJJ urban agglomeration is worse than single regions on urbanization development. • The obstacle factors of single regions and urban agglomeration are different. The Beijing(Jing)-Tianjin(Jin)-Hebei(Ji) (JJJ) urban agglomeration is one of the three major urban agglomeration in China, which plays an important strategic role in China’s regional development pattern. Based on the concern of inter-relationship within urban agglomeration, this paper creatively proposed a comprehensive gravity-Gram Schmidt Orthogonalization coupling model (CG-GSO) to quantitatively measure the urbanization development level at different regional scales. Compared with the information entropy method, the CG-GSO model was more reliable and fairer in evaluating the urbanization development of an urban agglomeration in the inter-annual dimension. We used the obstacle factor model to find out important ways to realize sustainable development at different regional scales. According to the trends from 2003 to 2017, the urbanization development levels were predicted by using the gray forecast model at different regional scales during 2018–2030. There was an upward trend in urbanization development at different regional scales. Compared with the internal single regions, a high starting and slow developing trend was in the urban agglomeration. In Beijing, the obstacle factors in urbanization development were in the demographic, social and eco-environmental subsystems. However, the obstacle factors were in the economic, eco-environmental and social subsystems in Tianjin, Hebei and JJJ urban agglomeration. The forecast results showed that urbanization development was going strong in internal regions from 2018 to 2030, while the overall urbanization development was slow in urban agglomeration. Urbanization development should focus on labor redistribution, weakening the boundary on social welfare, improving the efficiency of economic development and paying attention to protecting eco-environment for taking the sustainable development road in the JJJ urban agglomeration.