Saikyō Line is the name used for a train service running between Ōsaki and Ōmiya. The name is an abbreviation of Saitama 埼玉- Tōkyō 東京.
As Saikyō Line uses tracks of other lines all the way, it's not considered as an official railway line. At this site the term "virtual line" is used for such lines.
The service runs parallel to Yamanote Line between Ōsaki and Ikebukuro, using the Yamanote Freight Line tracks, and is the only service using Akabane Line and the Tōhoku Hon Line section Akabane - Musashi-Urawa - Ōmiya.

Akabane Line is usually referred to as Saikyō line as the line is only used by Saikyō Line trains. The traffic pattern is described in the Saikyō Line section above.

This section of the Tōhoku Hon Line is usually referred to as Saikyō line as the section is only used by Saikyō Line trains. The traffic pattern is described in the Saikyō Line section above.