4.2. WATT Accessibility
shows a remarkable time-space contraction across entire China by 2030. The average WATT accessibility among all cities decreased from 18.7 h to 13.1 h (an improvement of 29.8%) in the first period (Scenario 2/1), and will further drop to 10.3 h (a reduction of 21.4%) in the second (Scenario 3/2). Clearly, the reduction rate of travel time reduction in the first period is much faster than that in the second period.
At the regional level, the high accessibility regions are distributed in Central, East and North China in all three scenarios (the average WATT values lower than the national average). In Scenario 2/1, remarkable improvements to the HSR network occurred in the Northeast (38.5%), North (33.4%), South (32.6%) and East China (32.2%). The relative changes in the South (27.4%), Northwest (26.5%), Southwest (20.9%) and Northeast (20.8%) regions of China are large in the second period, which will mitigate the deficiencies from the first period. Hence, the rates of change in the accessibility of regions are balanced (37.6–51.1%) after the construction of the current and planned HSR network.
Similar results derived from provinces and the relative improvements of accessibility for all provinces are noticeable and balanced (39.6–56.3%), except for Tibet (21.0%), with the expansion of the HSR network in Scenario 3/1. In all three scenarios, the provinces with better accessibility are Henan, Anhui, Hubei, Jiangsu, Shandong and Jiangxi Provinces in the Central and East China regions. As expected, Xinjiang and Tibet have remained low accessibility, although the absolute change in travel time of Xinjiang Province is the greatest, with a reduction of 17.5 h (40.5%) overall. In the first period, the area of high accessibility expands to Beijing, Shanghai and Tianjin municipalities and Zhejiang, Hebei Provinces and then to Chongqing and Shaanxi with the expansion of the planned HSR network in the second period.
Although the expansion of HSR network improved the average accessibility across the nation, it slightly aggravates disparities between regions, between provinces and between cities. The regional CV value of WATT increases from 26.3% in Scenario 1 to 30.4% in Scenario 2, and then decreases slightly to 27.6% in Scenario 3, suggesting an increase of spatial imbalance between regions. The CV value of WATT between provinces increases from 41.7% to 50.6% during the first stage of the HSR network development and the disparity will be further aggravated with the future HSR network extension in the second period (53.9%). This reveals a similar trend given that the CV values between cities from Scenarios 1 to 3 are 43.5%, 50.8% and 54.0%, respectively.
The CV values between provinces in each of the regions (Table 2
) show that internal inequalities in Southwest and Northwest China are high in Scenario 1 and continue to increase as a result of current and planned HSR networks in Scenarios 2 and 3. In contrast, the disparities in East and Central China regions are low before the construction of HSR and they continue to decrease with the expansion of the planned HSR network. Clearly, disparities between the provinces in South China exhibit a different trend to other regions, increasing in the first period and then sharply decreasing in the second period. In contrast, the CV values for North and Northeast China remain almost unchanged in Scenario 3/1.
Accessibility maps for China, as measured by the WATT indicator, in the three scenarios are shown in Figure 7
a–c. The most accessible cities are mainly concentrated in the southeast of the ‘Hu Line’ and near to the geometric center of China. The map (Figure 7
a) exhibits a ‘core-periphery’ structure in Scenario 1 before the construction of HSR. In Scenario 2 (Figure 7
b), the contours generally spread outwards and the area of accessibility between 10 h and 12 h significantly extends from 0.3 to 1.2 million km2
(a three-fold increase). The planned HSR network causes the contours to spread further in Scenario 3 (Figure 7
c) and the area accessible in less than 10 h using HSR will expand from 1.1 to 2.4 million km2
(118.2%), accounting for 25.0% of China’s total area.
The absolute changes in accessibility (travel time savings) are shown in Figure 7
d–f. The map (Figure 7
d) shows that cities in the peripheral Northwest and Northeast regions receive relatively higher travel time savings in Scenario 2/1, for example, Urumchi (13.2 h) and Harbin (11.2 h) and changes in travel time of between 4 and 6 h occur for most of the area (4.3 million km2
). In Scenario 3/2 (Figure 7
e), the improvements in accessibility are less than in Scenario 2/1 and the area of all intervals is balanced (2.4–2.6 million km2
). Cities with much larger increases in accessibility are always distributed in Xinjiang Province (Figure 7
f), followed by parts of Northeast, Southwest and South China regions overall, such as Urumchi (19.5 h), Haikou (13.6 h), Harbin (13.0 h), Kunming (11.5 h), Changchun (11.4 h) and Xining (10.7 h).
4.3. DA Accessibility
lists the DA accessibility for all provinces in the three scenarios. The average number of reachable inhabitants within the 4 h limit of all cities in China rises from 61.1 million to 78.5 million (17.4%) in the first period, with a subsequent increase to 109.1 million (30.6%) following the implementation of the planned network in the second period and an increase of 78.6% overall (Scenario 3/1).
Regionally, the results from the DA indicator have some features in common with the WATT indicator: Central China, East China and North China have a higher accessibility in all three scenarios, for example, Henan, Anhui, Jiangsu, Shandong and Hebei Provinces and all four municipalities (Beijing, Tianjin, Shanghai and Chongqing). Conversely, Northwest, Northeast and part of the Southwest regions have lower accessibility, particularly in vast areas with a low population density such as Tibet, Xinjiang, Qinghai, Heilongjiang, Ningxia, Gansu and Inner Mongolia. With a few exceptions, absolute improvements in accessibility will also be strengthened in North China (84.4), followed by Central China (75.7) and East China (73.3) by the development of the present and planned HSR networks. The most notable gains are projected to occur in Beijing (140.1), Tianjin (110.1), Anhui (109.2) and Shandong (102.0).
The disparities in accessibility between regions and between provinces, according to the DA indicator, both deepen in the first period and will be somewhat reversed in the second period. The regional CV value increases from 56.8% to 60.4% in Scenario 2/1, with a subsequent decrease to 57.3% by the completion of the HSR plan in Scenario 3. In contrast, the provincial CV values of Scenarios 1 to 3 are 69.7%, 72.7% and 69.1%, respectively. This means that although the current HSR enlarges inequalities of accessibility, the proposed HSR network slightly enhances equitable accessibility between provinces. The CV value between cities increases from 76.6% in Scenario 1 to 79.7% in Scenario 2 and then increases slightly to 80.5% in Scenario 3.
The series of maps (Figure 8
a–c) indicate that DA values are high on the southeastern section of the ‘Hu Line’ and low at the edges. There are a smaller number of cities (87) with DA values exceeding 100 million inhabitants before the construction of HSR. This number increases gradually and reaches 118 in Scenario 2 and 161 in Scenario 3 by the completion of proposed HSR network. The maps of the absolute changes (Figure 8
d–f) show an obvious ‘corridor effect’ [23
], in that the top cities with respect to accessibility changes are mainly concentrated along HSR lines. The distribution of the gains is consistent with accessibility such that the central and eastern regions along the primary HSR corridors, especially at the intersections of HSR lines, experience much greater improvements in accessibility. However, few gains take place in the peripheral provinces such as Tibet and Xinjiang.