All the lines are and will be operated by the Daegu Metropolitan Transit Corporation (DTRO). Another line will operate in a few years as a heavy rail system using the Gumi–Daegu–Gyeongsan section of Gyeongbu Line. Line 4 is a long-range plan and will be a circle line. Fare is 1400 won and 1250 won with a prepaid card. There is a free interchange scheme between the metro and bus within an hour of first use for the prepaid card users. There are two types of buses which are local and limited express. Limited express buses have more seats, but often passengers are required to stand. , Local bus fare costs around 1,400 won, Limited express bus fare would set you back around 1,800 won. Discounted fare is available with a prepaid card. Bus route numbers are made up with 3 digits, each number indicates the area that bus serves. For example, number 407 bus runs from zone four, to zone zero, and then to zone seven. Other routes, usually circular, are named for the districts they serve and numbered 1 through 3. Traffic is sometimes heavy, however, the major thoroughfares handle fairly high volumes of traffic without too much trouble. Daegu is served by Daegu International Airport, located in northeastern Daegu. International destinations include Japan, China, Southeast Asia, and Vladivostok. Daegu is twinned with the following locations: