Model

Trail Network Representation

Network 
    Waypoints[]
        + AccessPoint (is this a place rides typically start)
    TrailSegments 
        + StartWaypoint
        + EndWaypoint
        + Trackpoints[] (minus time component?)
        + Trail (think tagging so consumers can name trails, note difficult sections, etc...)

Simplified for prototyping:

Network
    TrailSegments : Tracks (minus time component of trackpoints?)
        + StartWaypoint
        + EndWaypoint
        + Trackpoints[]

Input:

Track[] (basically a collection of individual rides, analogous to GPX track concept)