Cresston V4 was a beta route and is not the final, completed product. This manifested itself in a number of different ways. Parts of scenery are missing and some areas are in a grubby state. In order to provide some order to the chaos, some areas will have a billboard above the track stating that this is still a WIP area. As this is a beta, some signalling, speed limits, track properties and other track related items are still missing. This has an obvious impact on scenario creation, however, it is still safe to create scenarios in most areas.
Despite the billboards stating some areas are a no go, many areas of scenery beyond these boards are actually complete and you are more than welcome to go beyond them and take a look around, much of the idea behind releasing an open beta is in order to give people the chance to take a look at what was to come.
Despite it being unlikely that further development on Cresston will take place, i've decided to keep it available to download as according to posts on various forums, it's still enjoyed by many and is where it all started for me.