Along The Train Line
noun, の adjective
To run alongside the line (referring to the train line) means along the train line. What's along the train line? All kinds of things if you look carefully.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
私の弟は、京王沿線に住んでいます。
My brother is living along the Keio Line.