在来線

Etymology
Compound of. Originally, this referred to any existing line when a new line was built that served roughly the same area. While this meaning persists, with the advent of the shinkansen, the term gained a meaning in certain contexts to refer to the conventional railway lines as opposed to the bullet train lines.

Noun

 * 1) an older or pre-existing rail line, as opposed to any newer line servicing the same area
 * 2) the non-bullet train JR railway lines, the regular train lines as opposed to the shinkansen