I have a ticket for a conventional railway line. Can I take the Shinkansen instead (or vice versa)?

I had this question earlier so I did my research, and I thought some people might eventually ask the same question. The answer is: likely, if you’re not doing crazy things to your ticket. The details are a bit tedious, but it concerns a basic principle of JR ticketing, "Shikansen and conventional lines are seen as equivalent" (in Japanese, shinzai dо̄ichishi 新在同一視). Hereafter, we will simply call this the "equivalence rule".

Historically, Shinkansen lines were constructed to replace (and complement) the existing main lines (kansen) for long-distance travel, and that is how they got their name. Thus, Shinkansen lines and the conventional line running in parallel with them are deemed the same line by JNR (and the successor JR companies) for ticketing purposes. There are three Shinkansen systems with parallel conventional lines:

• the Tо̄kaidо̄/San’yо̄/Kyūshū Shinkansen: Tо̄kaidо̄ Main Line, San’yо̄ Main Line, and Kagoshima Main Line
• the Tо̄hoku Shinkansen: Tо̄hoku Main Line
• the Jо̄etsu Shinkansen: Tо̄hoku Main Line (Tо̄kyо̄~О̄miya), Takasaki Line (О̄miya~Takasaki), Jо̄etsu Line (Takasaki~Nagaoka), and Shin’etsu Main Line (Nagaoka~Niigata)

The following Shinkansen systems do not have parallel conventional lines according to the rules, even though conventional lines may technically parallel them:

• the Hokkaidо̄ Shinkansen, because there are no longer regularly scheduled passenger services running on the Kaikyо̄ Line. The Tsugaru Line (Aomori~Tsugaru-Futamata) is technically parallel since Tsugaru-Futamata is next to Okutsugaru-Imabetsu, but JR considers them different stations for almost all purposes, so this segment is not considered a parallel conventional line segment¹;
• the Hokuriku Shinkansen. Segments of Shin-etsu Main Line (Takasaki~Yokogawa, Shinonoi~Nagano) do run in parallel to the Hokuriku Shinkansen, but the intermediate sections have either been abandoned or transferred to Shinano Railway, so it’s meaningless to make it a parallel conventional line segment;
• the recently opened Nishi-Kyūshū Shinkansen.

If part of a ticket’s route is one of those "parallel Shinkansen lines", the Shinkansen can be taken instead.

Example: I have a base fare ticket (jо̄shaken 乗車券) from О̄saka (city zone) to Okayama. When I bought the ticket, I intended to use the Shinkansen, but now I’d like to use the express trains on the Tо̄kaidо̄ Main Line and San’yо̄ Main Line instead. I can do this, because the Tо̄kaidо̄ Main Line and San’yо̄ Main Line runs in parallel with the San’yо̄ Shinkansen. OTOH, if I have a conventional line ticket (which would have something like 東海道・山陽本線経由 printed on it) and I didn’t do strange things when I bought the ticket, I can still use the Shinkansen, provided that I buy a limited express ticket (tokkyūken 特急券).

Exception 1: the San’yо̄ Shinkansen runs in parallel between the San’yо̄ and Kagoshima Main Lines between Shin-Shimonoseki and Hakata. However, for various reasons, the fares on the Shinkasen and on the conventional lines are different, so they are not considered equivalent for all purposes. The only exception is that you can get a round-trip ticket (往復乗車券) even if one leg is via the Shinkansen and the other conventional lines.

Exception 2 (special intervals): Shinkansen lines and existing conventional lines do not parallel each other completely, and JR consider Shinkansen lines and conventional lines equivalent only if they actually run in parallel. There are 16 intervals in which Shikansen lines and their "parallel" conventional lines do not actually run in parallel, and if the starting point, ending point, or a connection point of your trip is located within one of those intervals, the equivalence rule does not apply when you are in this interval. Which means you can do things that are not normally allowed, such as backtracking.

The 16 special intervals are (the endpoints of the intervals are not included):

• on the Tо̄kaidо̄, San’yо̄ and Kyūshū Shinkansen (& the parallel conventional lines), between: Shinagawa~Odawara, Mishima~Shizuoka, Nagoya~Maibara, Shin-О̄saka~Nishi-Akashi, Fukuyama~Mihara, Mihara~Hiroshima, Hiroshima~Tokuyama, Hakata~Kurume, Chikugo-Funagoya~Kumamoto;

• on the Tо̄hoku Shinkansen (& the Tо̄hoku Main Line), between: Fukushima~Sendai, Sendai~Ichinoseki, Ichinoseki~Kitakami, Kitakami~Morioka;

• on the Jо̄etsu Shinkansen (& the parallel conventional lines), between: Kumagaya~Takasaki, Takasaki~Echigo-Yuzawa, Nagaoka~Niigata.

Example: I want to go from Okayama to Gifu. To do this, I want to pick up a connection at Nagoya. Now, without the special intervals rule, the segment from Nagoya to Gifu would be backtracking and won’t be allowed on one single ticket.

However, since Gifu is in the Nagoya~Maibara exceptional interval, it is not considered backtracking, and we can do this on a single ticket: the operational distance is simply Okayama to Nagoya (366.9 km) plus Nagoya to Gifu (30.3 km), i.e. 397.2 km, and the fare is 6,480 yen.

Note that if we change to conventional lines in Maibara instead of Nagoya, the operational distance would be Okayama to Maibara plus Maibara to Gifu (which will be equal to Okayama to Gifu on the Tо̄kaidо̄ Main Line). The distance is 333.4 km and the fare is 5,620 yen.

Exception to exception 2 "selective riding" (sentaku jо̄sha 選択乗車). This is a system where, when your designated route contains one or more of some 57 segments designated by JR, you have some freedom in choosing your route, subject to the usual limitations. This means that sometimes you can use the Shinkansen instead even if the trip is for a designated non-parallel interval. It is very complicated, so I move it to the end of the answer.

Exception 3 (Shinkansen within large city zones): There are five "large city" zones (大都市近郊区間) designated by the JR companies. For travel within one of those zones, passengers can (1) travel using any route regardless of the designated route and pay the same fare, subject to the no backtracking and no loops rules as usual (in practice, this means one always pays for the shortest route), and (2) no stopovers are allowed. Nevertheless, with only two exceptions, large city zones do not contain the Shinkansen routes otherwise completely within those zones. The two sole exceptions are the intervals between Maibara and Shin-О̄saka, and between Nishi-Akashi and Aioi (both are within the О̄saka large city zone).

However, for travel within large city zones, the equivalence rule still applies. In fact, both rules apply, making the situation very complicated. But, in short:

• if a ticket for a conventional line is purchased, you may not use the Shinkansen unless the Shinkansen route is considered equivalent to the route designated on your ticket, or part thereof. Even if you use the Shinkansen, the normal rules that apply to travel within a large city zone still hold.

• even if only part of a ticket’s designate route contains a Shinkansen route, the trip will be deemed to be not within a large city zone. The normal rules of route selection and stopovers apply. The Shinkansen equivalence rule still applies as usual, so one could use this exception to circumvent some of the large city zones rules, without actually intending to use the Shinkansen. See, e.g. this page (in Japanese).

Example: I have a ticket from Odawara to О̄miya, and my base fare ticket has the following designated route (the last line, in Japanese, is what would be printed on the ticket):

Odawara – (via Tо̄kaidо̄ Main Line) – Chigasaki – (via Sagami Line & Yokohama
Line: Sagami Line) – Hachiо̄ji – (via Hachikо̄ Line & Kawagoe Line: Hachikо̄
Line) – Kawagoe – (via Kawagoe Line) – О̄miya
経由：東海道・茅ヶ崎・相模・横浜線・八王子・八高・川越

(Note: this is extremely unpractical.)

Since my travel is within the Tоkyo large city zone, I may use any route that does not involve backtracking. So, I might as well use the more practical route: take Tо̄kaidо̄ Main Line through-service train, which would comfortably take me to О̄miya.

Now, I might want to save even more time and take the Shinkansen. I can take the Tо̄kaidо̄ Shinkansen to Tо̄kyо̄, then transfer to the Tо̄hoku Shinkansen. But with the ticket above, we cannot do so, because the Tо̄kaidо̄ and Tо̄hoku Shinkansens are not part of the Tokyo large city zone.

However, if we have the following itinerary, we can use the Shinkansen instead:

Odawara – (via Tо̄kaidо̄ Main Line: Tо̄kaidо̄ Line) – Tо̄kyо̄ – (via Tо̄hoku
Main Line: Keihin-Tо̄hoku Line) – О̄miya
経由：東海道・東京・東北

Example: Suppose I want to get to Odawara from Matsumoto using the Super Azusa Limited Express, but I don’t want to do it in one day. Since both Odawara and Matsumoto are in the Tokyo large city zone, we normally can’t do this on a single ticket. However, we can abuse the equivalence rule to get a stopover, as Odawara and Matsumoto are over 200 km apart by rail.

To get the stopover, we buy a base fare ticket with this itinerary without any intention to actually use the Shinkansen:

Odawara – (via Shinkansen) – Tо̄kyо̄ – (via Chūо̄ Main Line) – Shinjuku – (via Chūо̄ Main Line & Shinonoi Line: Super Azusa) – Matsumoto
経由：新幹線・東京・中央・篠ノ井

Since this trip consists of a Shinkansen segment, it’s not contained within the Tokyo large city zone. As this itinerary is more than 200 km, stopovers are allowed, and the ticket is valid for 3 days.

But the Tо̄kaidо̄ Shinkansen and Tо̄kaidо̄ Main Line run in parallel between Tо̄kyо̄ and Odawara, so we may (ab)use the Shinkansen equivalence rule and use the Tо̄kaidо̄ Main Line instead. Then, we can take a stopover in Tо̄kyо̄ and stay for a night. The next day, we buy a limited express ticket, get to Shinjuku, and catch the Super Azusa there. But note that we will no longer be able to use any route within the Tokyo large city zone: we must stick to our itinerary instead.

However, there is one exception to this exception! Even if your ticket doesn’t contain a route parallel to the Shinkansen, you may use the Shinkansen between Tokyo and Ueno and Tokyo and Shinagawa. This is utterly useless in most cases, but is allowed by the rules. The rationale behind this is Article 70 of the JR Conditions of Carriage: Ueno~Tokyo~Shinagawa is contained within the "Great Commuter Rail Loop" (densha dai-kanjо̄-sen 電車大環状線) which is a bit larger than what is enclosed by the Yamanote Line (see this page for a picture). If your trip begins and ends outside the loop, the route within the loop is not designated, and the fare charged is always the minimum possible. The loop doesn’t exclude the short Shinkansen segments within, so technically you are allowed to use the Shinkansen between Ueno and Shinagawa.

Finally, a personally tested example:

Example (personal): I have a base fare ticket from the Osaka city zone to Matsuyama with a connection in Okayama. The itinerary states that I will the San’yо̄ Main Line, Honshi-Bisan Line and the Yosan Line, in succession. Moreover, I want to get stopovers in Himeji and Okayama to see the Himeji Castle and Kōrakuen Garden. However, for the Osaka (city zone) to Okayama part, I decided to take the Shinkansen later.

So, I go to Shin-О̄saka and buy two Shinkansen limited express tickets there: one for Shin-О̄saka~Himeji, and one for Himeji~Okayama (note that limited express tickets do not allow stopovers). I take the Shinkansen to Himeji, leave the station, tour the castle, and come back to take the Shinkansen to Okayama. I get another stopover there, tour the garden, and finally come back to catch the Shiokaze Limited Express train to Matsuyama. Since none of my connection points are in a special interval, I do not have to worry about fares. Easy peasy.

Selective riding continued: This rule is considered extremely confusing even among Japanese railway enthusiasts, so let me try to illustrate it with an example.

Example: According to Art. 157, no. 27 of the JR Conditions of Carriage, selective riding is allowed when one travels from beyond Maibara (on either of the Tо̄kaidо̄ or the Hokuriku Main Lines), and either to Gifu-Hashima, or to somewhere beyond Gifu (again, Tо̄kaidо̄ or Takayama Main Lines). Here, "beyond" means including the said station. There is a handy diagram taken from the official JR rules:

Now, since selective riding is allowed for this segment, a ticket that goes from Maibara (or beyond) to Gifu-Hashima is also valid for travel to Gifu, and vice versa, even though the two lines here are not equivalent. Selective riding is also allowed for the other direction, with the explicit exception that it does not apply when your trip begins somewhere between Nagoya and Kanayama (exception to an exception to an exception!).

You are also allowed to travel first to Gifu, then move on your own to Gifu-Hashima (or vice versa), and then continue your trip, provided that your ticket allows stopovers. Of course, if you’re merely in passing between Nagoya and Maibara, then you can choose to travel either through Gifu or through Gifu-Hashima (aka Shinkansen and conventional line).

These rules, in combination, create some "equivalences" between stations in that a ticket to/from station A is also valid for station B. One can also travel to A, and then travel by other means (or on another ticket) to B, and then continue from B. These are mostly to cope with the situation where a Shinkansen line has a stop nearby a conventional line stop but aren’t exactly "parallel".

Here’s a list of those equivalent pairs of stations; you’re welcome to refer to the quite informative diagrams that accompany the offical rules; unfortunately they’re written all in kanji. Of course, I assume constant direction of travel and no backtracking:

• Mizusawaesashi (Tо̄hoku Shinkansen) and Mizusawa (Tо̄hoku Main Line);
• Kurikoma-Kо̄gen (Tо̄hoku Shinkansen) and Nitta (Tо̄hoku Main Line);
• Shiroishizaо̄ (Tо̄hoku Shinkansen) and Shiroishi (Tо̄hoku Main Line);
• Jōmō-Kōgen (Jōetsu Shinkansen) and Gokan (Jōetsu Line);
• Honjō-Waseda (Jōetsu Shinkansen) and Honjō (Takasaki Line);
• Shin-Fuji (Tо̄kaidо̄ Shinkansen) and Fuji (Tо̄kaidо̄ Main Line);
• Gifu-Hashima (Tо̄kaidо̄ Shinkansen) and Gifu (Tо̄kaidо̄ Main Line). However, trips between Nagoya, Odobashi and Kanayama, and Gifu or Gifu-Hashima, are explicitly excluded;
• Shin-Kо̄be (San’yо̄ Shinkansen) and Kо̄be (Tо̄kaidо̄ Main Line);
• Shin-Onomichi (San’yо̄ Shinkansen) and Onomichi (San’yо̄ Main Line);
• Higashi-Hiroshima (San’yо̄ Shinkansen) and Saijо̄ (San’yо̄ Main Line);
• Shin-Iwakuni (San’yо̄ Shinkansen) and Iwakuni (San’yо̄ Main Line);
• Shin-Tosu (Kyūshū Shinkansen) and Tosu (Kagoshima Main Line);
• Shin-Ōmuta (Kyūshū Shinkansen) and Ōmuta (Kagoshima Main Line);
• Shin-Tamana (Kyūshū Shinkansen) and Tamana (Kagoshima Main Line).

Be careful that Shin-О̄saka, Shin-Yamaguchi, Shin-Kurashiki and Shin-Shimonoseki are not equivalent to their conventional line counterparts!

The rule also provides for a weaker form of equivalent station pairs, where:

1. the Shinkansen and its parallel conventional line are not parallel between A and B;
2. however, C (Shinkansen station) and D (conventional line station) in this section are located close enough (or serve the same area);
3. therefore, when travelling through this segment between A and B, one can travel to C, get off there, travel by alternate means to D (or vice versa), and continue the trip. Pairs of this form include:

• Sendai~Ichinoseki: Furukawa (Tо̄hoku Shinkansen) and Kogota (Tо̄hoku Main Line);
• Kitakami~Morioka: Shin-Hanamaki (Tо̄hoku Shinkansen) and Hanamaki (Tо̄hoku Main Line);
• Nagaoka~Niigata: Tsubamesanjō (Jо̄etsu Shinkansen) and Higashi-sanjо̄ (Shin-Estu Main Line)

Shin-Yokohama is also equivalent to Yokohama this way, but in two cases:

• either: one end of the trip is beyond Shinagawa, and the other end is beyond Odawara;
• or: only if one is travelling from the Tо̄kaidо̄ Main Line, one end of the trip is beyond Higashi-Kanagawa, and the other end beyond Odawara.

References:

1. JR East website: 運賃計算の特例
2. JR West website: 新幹線と在来線が並行する区間の特例
3. Japanese Wikipedia: 大都市近郊区間 (JR)

¹: not relevant here, but for the Seishun 18 Hokkaido Option Ticket, one is explicitly instructed to change for the Shinkansen at Tsugaru-Futamata. This is the only case where I know that JR expects one to make such a transfer.