Jiangsu is an east China communication center. Nanjing and Xuzhou are two rail clearing- houses. Passing through the province are the Longhai (Lanzhou-Lianyungang), Beijing-Shanghai and Nanjing-Wuhu railways. The completion in 1968 of the Yangtze River Bridge at Nanjing has helped improve transportation between north and south. Maritime shipping and inland navigation along the Yangtze River are well- developed. Lianyungang is the principal seaport, and Nanjing and Zhenjiang are large river ports. The length of highways in use is 14,000 kilometers.