This is not addressed by the city, so I want to use a good general standard.
Cul de sac radius? I use 45' radius, as the tightest.
But for the general curves, what is a good radius, and width?
Thanks
Nate
My favorite is 12,432,108 feet radius. It looks just like a straight line to anyone else.
57.30', or multiple thereof...
If the City sets no minimum contact the fire department. In the end many municipalities set minimums based on fire department needs anyway...
57.30'? is that the delta, or radius?
I don't do alot of this.... and I want to do this in such a way that it will work well with the world. Fire trucks, school busses, etc.
N
> If the City sets no minimum contact the fire department. In the end many municipalities set minimums based on fire department needs anyway...
this is correct.
Our county std is a 60' radius for a cul de sac; however something to consider is that the apparent rule of thumb around here for intersections with high truck volume is to use an 80' radius.
Two words: Green Book
https://bookstore.transportation.org/collection_detail.aspx?ID=110
57.295779' is the radius of a curve that delta is equal to the arc length.
Just easy to figger in the field.;-)
[sarcasm]45' ?!? sounds like you're designing for areas where the average mode of transportation is an ATV- 'cause the folks ain't a got a driver's license no' mo'[/sarcasm]
Now don't be using that degree of curve stuff!!!
That makes it too hard to put in the collector;-)
Nate:
What James said and remember the acronym AASHTO
As an aside: you are entering into the realm of engineering and probably should discuss this issue with one.
Also, every city/county I work with seem to have slightly different standards.
The surveyor needs to know this stuff, but in my region it is clearly engineering and much easier to use the local standards and don't go tighter without some sign off by regulators. There are good reasons for these and you will see it when a tractor trailer is making a turn on a too tight street intersection.
Just like everything else in the Garden State, they have regulated the heck out of this as well. It's all codified here:
http://www.state.nj.us/dca/divisions/codes/offices/rsis.html
and more specifically here:
http://www.state.nj.us/dca/divisions/codes/codreg/pdf_regs/njac_5_21.pdf
The PDF is searchable, so you can find stuff pretty fast. The regs actually do work out pretty well most of the time, and it usually comes out looking pretty good. You can search 'cul de sac' and there are a few different possibilities.
In my municipality they have a regulation that a dead end street (i.e. ending in a cul-de-sac) cannot be longer than 600 feet. This messes me up because my house is 900 feet from the road and I want to put in a street with a cul-de-sac ending near my house so that I can develop the property. If anyone could tell me what the reason is for this regulation, I may be able to ask for an exception. I know for sure there are dead-end streets nearby that are way longer than that, but they may pre-date the regulation. They are very tough to deal with, so just asking the reason why is probably not an option. They will just tell me "it is a regulation".
> As an aside: you are entering into the realm of engineering...
Maryland lets us play in their sandbox:
(k) Practice land surveying. --
(1) "Practice land surveying" means any service, work, documentation, or practice, the performance or preparation of which requires the application of special knowledge of the principles of mathematics, the related physical and applied sciences, and the requirements of the relevant law, as applied to:
(vi) in conjunction with the site development or subdivision of land, the preparation and design of plans for the following projects, provided that such preparation and design are in accordance with design manuals, details, and standards accepted by the State or local authority:
1. road and street grades;
2. sediment and erosion control measures;
3. nonpressurized closed storm drainage and stormwater management systems; and
4. open conduit storm drainage and stormwater management systems.
On the post topic, NC subdivision reg's are topography ("terrain")/ useage/ speed based:
NCDOT Subdivision Roads- Minimum Construction Standards
edit> page 26 is where the meat starts.
In NC, PLS can do roads using published standards (site specific design would take an engineer).
On the length question:
As I understand it, current trend (prolly near a decade 'roun here) in subdivision design is focused on incorporating traffic calming and congestion management fundamentals. In the case of cul-de-sac length, 500-600 feet is the 'magic' traffic calming distance.
I believe the hope is, by limiting to this distance, developers want be creating the next local drag strip and the neighborhood's value (translates to lifespan) could be better sustained.
In my necck of the woods, we have similar codes (500-ft) and they incorporate that into bigger developments, requiring intersections and/ or alternate access points to major/ minor arterials.
Buzzword is 'node'. Our designs are node-based in some areas.
If that clause was interfering with a client's (or my own) ability to develop land, I would try this:
A 600 foot cul-de-sac (your length, I think). Lots set out, appropriately. A 30-ft easement off the back of the cul-de-sac for a future minor subdivision. Or if code allows, the maximum number of lots beyond the sac that can be served by private easement. Yours being one lot, of course.
Have a good one,
C
They do allow more there.
I imagine that being allowed to do it means that you are going to do it, even if you'd rather not. Not saying you don't like that aspect, but I sure don't mind handing off the engineering for subdivisions to the enginerd;-)
Cool! I learned something. That is a good one to have in the memory bank. Jp
The general rule of thumb I was always told is they have to be big enough for a fire truck and/or school bus to turn around in.
Just how big that is, I don't know.
John, I've asked the same question too. It seems to be emergency vehicle related and fire hoses are only 300' or so long so they put the hydrant in the middle. Ask them about a private easement vs a public road, you have better luck.
Nates cul de sac radius question - seems 50 or 60 is about as small as I've seen. Same thought - fire trucks need that to turn around and not have to back up. And school busses
> If anyone could tell me what the reason is for this regulation, I may be able to ask for an exception.
What I've been told by planners (so take that at face value, or less) is this type of regulation is based on an algorithm using the number of residential units rendered inaccessible to emergency vehicles by a single choke point and the historical occurrence of multiple emergency calls in the same area.
Kind of like the joke (albeit dark) I heard a transportation planner say in response to a "how many people have to die before we get a stop light" letter to the editor..."well, the manual says six"
I remember that it takes around a 100ft wide space for an 80ft trailer house to make it thru a 90° turn.
I've used a 30ft radius for cul-de-sac on roads 600ft or so in length so the postman could turn around.
Norm is for the Radius to be the same as the incoming r/w width.
