How does one right-of way type change to another?
The transition from street to private right of way or vice-versa is simple: the tracks simply leave or enter the pavement. If they cross traffic lanes to do so, a crossing gate may be provided, but you dont have to worry about that. Entering a tunnel takes a short segment of depressed track. This may be in private right-of-way or even in the center of a street; in either case, traffic cant cross over this transition area. That means a downtown Houston block (300 ft.) is not enough space to make the transition. Likewise, it takes the tracks 500 ft. to go from being level to being elevated. This section is an elevated structure, but it does not have enough clearance to allow streets or railroad to cross underneath. An overpass- where the tracks go up, cross something, and go back down- must thus be at least 1000 feet long. See fig. 1.
