Radius in subdivision streets
Radius in subdivision streets
(OP)
In my firm we always design interior subdivision street 25' wide (including curb and gutters). Intersecting streets have a curb radius of 25'. I was walking through an old section of town and noticed that the curb radius was much smaller, probably between 5' and 10'. It made it a lot easier to cross the street. I have been thinking about reducing the radius for my next design but was worried about bus traffic. Does anyone else have any thoughts about this.





RE: Radius in subdivision streets
We designed subdivision roads either 28' (back of curb to back of curb) or 24' (boc-to-boc), with 25' corner radii. This was the planning commission/street department minimum, contained in the subdivision regulations.
I wouldn't go lower than 25' personally because it always annoys me when right-turns are difficult to make merely because of the damn turning radius. Depending on the type of neighborhood, school buses might be a serious consideration.
RE: Radius in subdivision streets
Locally we use a 7 m radius. We also use barrier curbs with a 1 m transition to the curved portion. If sidewalks then we use a dropped section in the barrier curb for pedestrians.
Rick Kitson MBA P.Eng
Construction Project Management
From conception to completion
www.kitsonengineering.com
RE: Radius in subdivision streets
RE: Radius in subdivision streets
As RDK says, you can go smaller using a tapered offset or 3-center curve. You can also reduce the radius if you have striped parking lanes, since the effective radius is a three-point curve tangent to the edge lines and the center of the corner curve.
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"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail."
Wm. Phelps Eno, ca. 1928
RE: Radius in subdivision streets
The reason the tight radius works in the old part of town is that the streets are wider than the new subdivision with parking lanes on both sides. Longer vehicles ( bus , garbage, delivery trucks ) typically complete their turn by encroaching over the lane next to the centerline.
Putting short radii on narrow streets means the rear wheels of turning vehicles track over the curb ….or they encroach into opposing lanes of traffic.
Bottom line: don’t design any radii unless you check it with turning templates
RE: Radius in subdivision streets
RE: Radius in subdivision streets
RE: Radius in subdivision streets