There are similar cases on private railways as well. You might think this is unique to the JR Group, but that is not the case—there are similar examples on private railways as well. One such example is the “Liberty Aizu” limited express, which runs directly from the Tobu Railway’s Kinugawa Line to the Noiwa Railway’s Aizu-Kinugawa Line and on to the Aizu Railway’s Aizu Line. The applicable section is between Kinugawa Onsen and Aizu-Tajima, and regulations stipulate that a ticket alone is sufficient for travel strictly within this section “only.” As I mentioned in my test ride report on the SL Taiju “Tsuchi,” the population along the Nōgan Railway line is particularly sparse, and ridership on local trains is low. Since operating local and limited-express trains separately would be inefficient and uneconomical, the limited-express trains serve as substitutes for the local trains.
A Limited Express Ticket Is Required for Travel Spanning Beyond the Special Exception Section: All special exceptions apply only to trips that are completed entirely within the designated section; if you continue on the same train beyond that section, a Limited Express ticket is required. This is only natural, given the intent of the rule. In some cases, a limited express ticket is required for the entire journey; in others, it is required only for the sections not covered by the special provisions. The former applies to the Muroran Main Line (Higashi-Muroran to Muroran), the Sekisho Line (Shin-Yubari to Shintoku), and the Ou Main Line (Shin-Aomori to Aomori). For example, if traveling between Aomori and Shin-Aomori, you can ride in the non-reserved seats of the “Tsugaru” limited express with just a local ticket for that section; however, if traveling between Aomori and Hirosaki, you’ll need both a local ticket for the Aomori–Hirosaki section and a limited express ticket. The same applies to the Tobu Kinugawa Line–Nōgan Railway Aizu Kinugawa Line–Aizu Railway route; when traveling through to stations south of Kinugawa Onsen, a limited express ticket is required for the entire journey. On the other hand, the two lines in Kyushu fall into the latter category. On the Miyazaki Airport Line, the limited express surcharge is calculated only for the section north of Miyazaki, which is outside the special exemption zone. Similarly, on the Sasebo Line between Hayaki and Sasebo, if you travel all the way to the east of Hayaki, the limited express surcharge is calculated only for the section east of Hayaki.
© Source travel watch