In the book of Acts, the followers of Jesus are called the followers of the Way (Acts 9:2; 19:9, 23; 22:4; 24:14,22). The name appears to reference Jesus’ teaching.
I am the way and the truth and the life. No one comes to the Father except through me. (John 14:6)
The narrow road is the Way on which Christ's followers attain Christ's holiness. It is the road of sanctificaiton. In His last prayer in Gethsemane, Jesus prayed for the disciples and those who will believe in Him through their message (John 17:20). He asked for complete unity of God and believers, that they become EHAD (John 17:22) just as God the Father and Jesus are EHAD (John 17:23). Jesus prayed for oneness of the believers with God as supposed oneness with the world. The distinction is in the state of heart of a believer in which Jesus Himself dwells (John 17:26). This is the essence of becoming EHAD with God. This is the Way of Holiness. The transformation into the image of Christ transforms the common into holy.