Transportation is provided by extensive networks of railways, highways, bus routes, ferry service and air routes that crisscross the country. Transport in South Korea is reasonably priced, quick and efficient. There are six largest cities in South Korea, all have subway system: Seoul, Busan, Daejeon, Daegu, Gwangju and Incheon. The subway is a convenient and cheap way of getting around these major cities. Since signs and station names are in both English and Korean, it is foreigner-friendly and easy to use. Frequent and inexpensive bus service is also provided. However, aside from the non-English speaking bus drivers, accessibility to English bus stop maps are also challenging. If you want to go to different cities, railway and domestic air service are both good choices. Most railway routes enjoy frequent service, with trains every 15-60 minutes connecting Seoul to all major South Korean cities. Although most Koreans travel between cities by express bus or train, air service between major cities increased, especially among business travelers.