China’s Ministry of Transport has revised upward sharply the cost estimate of a 55-kilometer-long bridge to connect Mainland China with Hong Kong city, by $1.5 billion. The new span’s cost is now pegged at $6.4 billion, the government says.

The project, which includes a bridge and a tunnel, will drastically cut travel time between Hong Kong, Macau and Zhuhai cities in China’s Pearl River Delta economic hub to one hour. At present, it takes four hours to travel by ferry between Hong Kong on the eastern side of the delta and Zhuhai on the western bank.