see these posts). The Korea Joongang Daily recently carried an article describing government plans to spend 74 trillion won or $62.2 billion on high speed rail development. As shown in the first graphic (click to see a larger version) the initial phase of the project will link five cities on the outskirts of the national capital metropolitan area. I will admit a strong personal interest in this project because it will reportedly reduce travel time from Songdo to Seoul from about an hour and a half to only 23 minutes.
The article also notes that "Outdated rail lines along the central and southern regions of the peninsula will also be upgraded.
It currently takes more than five hours to travel from Seoul to Gangneung, Gangwon, on the east coast by train. That travel time will be cut back to one hour and seven minutes. The time it takes to travel from Busan to Gwangju on the opposite site of the Peninsula will be reduced to two hours and 20 minutes from the existing six hours and six minutes." The second graphic illustrates the major national routes that will be in service upon completion of the project in 2025.