Ribbon Driveway Standards

[atxengr]

Hello,

I'm searching for design standards for residential concrete ribbon driveways. I've consulted Transportation and CE handbooks but didn't find any info. I have the specs for the driveway in the right of way and the intersection with the street, but would like to find some national or engineering society sanctioned design standards for the width of concrete ribbons and the median in between for residential passenger car driveways. So far I've only found municipal standards ranging from 18" to 30" in width.

I'm assuming that someone, somewhere "did the math" and determined what width and spacing a ribbon driveway should be. Any direct references would be very helpful.

Thanks.

Peter C. Brust, Ph.D., PE

 

[PELS]

Generally, ribbon driveway standards are governed by local jurisdictions, HOA's or local architectural design guidelines. I have not seen a nation standard.

Here is a local design standard. Scroll down to page 161 and read the text referring to Figure 149.

http://www.fpl.fs.fed.us/documnts/usda/ah73/ah73chapter5.pdf

 

[PELS]

Sorry. I meant Figure 148B.

 

[atxengr]

Pels,

Thanks for the reply.

I've already seen many local standards, including the one you cited, but I'm seeking a standard based on engineering data and design and not the whims of a local official. My city, Austin, TX, has recently come up with an unwritten standard for ribbon driveways stating that they should be a minimum of 36" wide. Of course this makes no sense because at 36" it would be easier to just pour a solid slab driveway. I should be able to get a waiver for a 24" ribbon design if I can find an engineering basis for doing so.

Like almost all design problems, someone must have already studied this issue and determined that given the width of passengers cars, tire size, ability of drivers to control direction, etc. there's a minimum and maximum width of the ribbons and median. I need to find such a study or standards based on it.

Any hints are greatly appreciated.

Thanks,


Peter C. Brust, Ph.D., PE

 

[ACtrafficengr]

Car magazine road tests list the track widths of vehicles tests. The inside dimension should accomodate subcompacts like Honda Fits and Chevy Aveos. The outside width needs to be wide enough for large SUVs and pickups. Add six inches on either side, and I wouldn't be surprised if you need 30" at least.

If the driveway is not straight, you also need to accomodate off-tracking of the rear wheels.

"...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

 

[ACtrafficengr]

What if your client buys one of these?

http://collectiblecars.nytimes.com/View_Listing.asp?ListingID=COL803221&From=F

"...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

 

[atxengr]

ACtrafficengr,

Thanks for the info. Actually, I can get data from the US DOT listing the widths of production cars/trucks sold in the country and determine the width required to accommodate, say, 90% of vehicles, but that won't solve my problem. I need a recognized source other than myself or other local jurisdiction to present to the city.

BTW: My "client" is myself. I'm just trying to avoid paving over my entire 70 year old gravel driveway and then some with asphalt or concrete. If the occasional car/suv/truck can't fit on the drive way it's not a big deal as most people in the neighborhood have used gravel driveways for a century or so.

Thanks again,

Peter C. Brust, Ph.D., PE

 

[swazimatt]

DOES THIS HELP?

http://www.cnci.org.za/inf/publications_pdf/driveway.pdf

 

[rday]

Why are you paving at all, if you have a perfectly functional gravel drive?

It is not likely you'll find some definitive federal guide for driveways. If you have to pave, I would compile as many local standards as possible and any other standard availible from any source. Local standards should ideally be from areas with similar characteristics (weather, terrain, population desnsity, etc.) This will yield some distribution of standards for comparison.

Having worked as a county engineer this is the type of research that would be done in developing any standard for addoption into local regulations. Think of it like this, when adopting a standard there is no need to reinvent the wheel. See what is out there and is successful and use it. If it turns out to be problematic it can be amended once it is in place.

If you are looking at getting a variance, you will need to show why the adopted standard should not apply, is unneccecsarily stringent or creates some hardship (beyond financial). I should note, an unwritten standard is not typically enforcable because is has not been adopted by local ordinance. Makes the fight easier.