Highwayland

If you have gotten this far in my site you probably would enjoy this article from the NCDOT titled How a Road Gets Built. Click below to read the article:
http://ncdot.org/construction/roadbuilt/
The article covers many aspects of the road building process from planning to final inspection.

Here you can see the construction of a detour bridge on Poole Rd. This is one of the roads that was previously used for the commute to Raleigh as an alternate to what is now US 64 Business (see Walk4). Now that the US 64 Bypass has opened the bridge replacement could be done without nearly as much aggravation to commuters.

There is a set of  two curves before the detour bridge and another set of two curves after the detour bridge. The first set of curves (at Tie In 1)  divert the traffic off of the permanent road (-L- line) and over the detour bridge. The curves in each set are equal in radius.

 

The first curve in the set flows directly into the second curve without any straight section of road (tangent) in between them. This makes a smoother ride for vehicles passing through the detour. After the end of the second curve there is a tangent to accommodate the detour bridge.

The second set of two curves brings traffic back to the -L- line at Tie In 2.

These diagrams were not drawn for Poole Road. These are basic illustrations of a bridge replacement with a detour on site. Hopefully from time to time I will improve these diagrams. Stay tuned.... and please feel free to email me with questions or comments if you have any. If I don't know I will try to ask someone who does know or look it up.

Pilings being set for the detour bridge

The traffic will be routed off of the old bridge and onto the detour bridge so that const- ruction can begin.

Here you can see the transition between the detour (dark asphalt) and the permanent road (lighter asphalt). The elevation of the detour pavement has to be exactly the same as the elevation of the old pavement for a smooth transition. In addition they have to have the same or very close to the same superelevation (see Walk 4).

In the picture above you are standing before the first detour curve as it transitions from the existing pavement to the new detour pavement and leaves the permanent road. Exactly where the first curve ends, (a little after the edge of the new detour pavement) the second curve begins.