I've found it is the local juristiction that governs the driveway radius, as well as spacing between drives and placement respective to turn lanes, opposite drives, etc.
A 15'or 20' radius for a commercial drive seems to be about standard.
GoldDredger is correct. Check with the local juridiction
The radius for a residential drive is 5' to 10' radius.
In addition, the book Architectural Graphic Standards by Ramsey has driveway layout guidlelines. You have to determine the type of vehicle that will be using the driveway. Then you look up the turning radius and dimensions.
That's what I thought. I see alot of 15' radius's and 25' radius's. So local ordances and/or DOT standards are the best reference? Maybe I was thinking to hard...LOL
The best person I think is calling the inspector for the city you are working in. Let them know what you are doing so he somewhat remembers. Or check the local city website for their driveway manual.
CDG, Los Angeles Civil Engineering specializing in Hillside Grading
If you are connecting to a state highway, forget anything the city says and go with exactly what the state says. Here in California, Caltrans rules all.
CDG, Los Angeles Civil Engineering specializing in Hillside Grading
Brandoncdg is on the right track. Find out what agency has jurisdiction over the road. You may need to get a highway work permit for any construction within the right-of-way.
We use 15' radii for residential driveways and 34' radii for commercial driveways. Most of our roads are rural or suburban, so smaller radii mentioned above are probably needed in urban areas. You can also get away with a smaller radius if you have a shoulder or parking lane.
"...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
"I'm searching for the questions, so my answers will make sense." - Stephen Brust
Another thing to throw in there. Depending on what you do on your road can trigger more things having to be built in the road. So depending on what you are designing you may want to ask if I do this, does it cause anything special to happen?
CDG, Los Angeles Civil Engineering specializing in Hillside Grading
I don't know all the details of your design but if you are connecting to an existing road or highway, make sure your topo is up to date. I make an effort to visit every site (should be more like a rule) and many times I end up seeing physical features that either were not included in the collected survey data or are a little trickier to see on your computer screen.
What I mean, is that while you are trying to meet a certain driveway spec or requirement, you may have electric vaults, meter boxes, etc in the way and that could create even more design issues for you. This is basically along the lines of the last post by brandoncdg.
Sometimes a meter box or vault might be located just behind the curb and the new drive would be proposed right over it.
The meter box or vault might have originally be designed for landscape applications, and now needs to be traffic rated. Or possibly the juristiction will want you to move it outside of the proposed drive altogether. Either way it will have to be re-set.
Quite possibly sewer cleanouts could be there as well, needing to be re-set into the new drive.
Even worse, a big power or telephone pole right where your drive is proposed.
Happens ALL the time. CPENG78 is pointing out it is prudent to field visit your site just to be sure. I would.
Yes, like GoldDredger mentions, my point was only to field visit your site as a precaution. You may something that needs to be addressed in your design and you may not find anything of concern at all. Of course we all prefer the latter.
However even if you don't find anything, next time you meet or speak with the client or other consultants, your field visit gives you an edge over those discussing potential issues.
The turning radii will be determined by the AASHTO design vehicles recommended by the city fire marshall and enforced by city engineering. It is possible to challenge a particular radius if you can proved that a tighter radius can work...this can be done by demostration..(i.e. template overlay, AutoTurn, etc.).
BTW a useful thing to use to do a quick walk around the ROW of a site is by using google maps and zooming into street level. I was able to look through one of our large project's surveys and this to get a good idea of what was out there before I really need to walk the site. We have to move almost every vault, pole, etc. because they are dedicating the street and moving driveways around.
Were you able to find the standards by going to the Public Works website or anything like that?
Civil Development Group, LLC
Los Angeles Civil Engineering specializing in Hillside Grading
AutoTurn is a very cool program to model vehicle maneuvers. I have use it in a CAD platform (I don't know if there is stand alone version) which allows me to maneuver a vehicle directly on my site to simulate turning movements. It has pretty much every vehicle that you can imagine with some models included in the program and other models that you have to purchase separately. Not that I am endorsing it, but you can see how the program works at their site
It also has options to design your own vehicle with turning capabilties per your specification.
I have used mainly for fire truck turning movements, but it has also come in handy in the design of driveways, delivery dock areas, parking lots and I believe with have a project coming up with STAA trucks.
I also agree, google maps and streetview has also come in handy for me as well specially in the early planning stages of a project. Technology has certainly added another tool there for pre-design purposes. In many situations, it has prepared for what to look for during a site visit.
AutoTurn is great to design driveways because you have backup in case anyone questions you. Just make sure to clarify with you Client what truck turning template you are using so everyone is on the same page.
Also, if you use Autoturn, make sure you become familiar with the maximimum steering angle setting. It can be adjusted by the user and if set to an unrealistic value, it can create inaccurate results.
In other words, if the user does not check all of the settings and adjusts for the actual vehicle being tested, the results of Autoturn may indicate that (by the computer model) a vehicle can access a site, when in reality the "real" vehicle cannot.
