The length and extent of the Hobbiton Road isn't explained in detail. All we can say for sure is that the road was known as the Hobbiton Road at the point where it ran past the Bywater Pool, westward of Bywater itself on the way to Hobbiton. Before this, the southern section of the same road (from the East Road to Bywater) is named as the Bywater Road. The most natural assumption would probably be that the road was the 'Bywater Road' until it passed through Bywater, at which point its name changed to the 'Hobbiton Road'. However, this arrangement is far from definite; as an alternative, it might be taken that 'Bywater Road' and 'Hobbiton Road' were simply different names for the same stretch of roadway.