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cehall (Mechanical) (OP)
17 May 04 11:22
We are finishing a driveway on the new property.  So I thought I would ask the "civil" forum for help.

The driveway goes straight back and then has a oval loop.  The loop is 100-125' high.  I found design info on Cul-de-Sac Designs.  Seems the 30' min radii so too small and the 40' radii with center island would work nicely.  I can actually go 50' on the inside.  Getting the 20' lanes down the sides and a wider, say 25', lane on the top is okay.

It is just the tree hugger in me that wants to keep the 40-50' inside radii.  I just don't know if it is enough for the future vehical designs.

The loop island looks so nice now and if I make the inside radii bigger I start taking down 12"+ dia trees that would be in the new back yard... that turns into a back "driveway".
RWF7437 (Civil/Environmental)
17 May 04 13:11
You didn't ask a question.

There is a program available called Autoturn which contains numerous templates for many sizes and types of vehicles    ( including aircraft). The program is expensive but the plastic templates should be reasonably priced.  Do Google search on "autoturn".

Good luck
dicksewerrat (Civil/Environmental)
17 May 04 13:12
Your local DOT and or traffic engr. should be able to help. ASSHTO would want you to pay for this I think.
cehall (Mechanical) (OP)
17 May 04 13:18
Is 27' inside radii large enough for a truck pulling RV?  The lead in/out lane can be 22' and the top of the oval is 36'.
RWF7437 (Civil/Environmental)
17 May 04 13:23
Please ! go find a open area or parking lot and actually measure the minimum inside radius your vehicle combination is capable of.  No one on this forum can answer your questions with the information provided and without a scaled picture of what it is you're trying to do.

Good luck
cehall (Mechanical) (OP)
17 May 04 13:26
Sorry to waste your time ...

I just don't have any way to measure some future vehicle.
RWF7437 (Civil/Environmental)
17 May 04 18:56
Why not visit some RV parks in your area ?  Look around. Observe curve radii. Measure them.  Visit RV dealers and get specifications and brochures on RVs, including turining radii bot backwards and forwards.
Helpful Member!  TerryScan (Civil/Environmental)
18 May 04 10:46

AASHTO's "A Policy on Geometric Design of Highways and Streets" (known as "the green book") has a design vehicle called P/T which is a 19ft long passenger car with a 27 ft. camper trailer.  The turning template for this vehicle shows a 33 ft. min. outside wheel path. It appears one could have a center radius as small as 16 ft. (concentric with 33 ft. circle).

Wider paving does give more room to maneuver.  If one makes a inside radius larger than 16 ft., be sure to expand the outside radius (if one maintains 18 ft. min paving width, probably OK)

If one is envisioning a larger design vehicle, things change.  A tractor trailer (AASHTO WB-50) should be able to handle a circle with a 25' inside paving radius and 55' outside radius.
TerryScan (Civil/Environmental)
18 May 04 10:57
I took another glance at the green book.  If, you are considering a Motor Home, it adds another dimension.  It would require about a 42 ft. outside radius and approx. 25ft. inside.  A Motor Home with trailer wouldn't be too different from the tractor trailer - could perhaps tolerate 30' inside radius instead of 25'.
cehall (Mechanical) (OP)
18 May 04 11:02
Thanks TerryScan!  That is great news.

The 33' (or 27') inside radius would work then.

I have 18-20' wide lanes at sides of oval and a 36' high lane at top.  So they would also work.

I am so glad I don't have to take down another 18 8-14" trees plus all the little stuff.
cehall (Mechanical) (OP)
18 May 04 11:12
Thanks again TerryScan!

We have worked hard on this 700' driveway with loop.  I was hoping that we were getting it to where we could stop cutting down trees.  And start putting down the initial base layers.
TerryScan (Civil/Environmental)
19 May 04 10:26
Your welcome.  I would also consider the all the other advice already given, especially checking local RV dealers to get info on possible models you may purchase.
rmw (Mechanical)
19 May 04 12:07

Some vehicles have different turning radii depending upon which direction they are turning, right or left.  It might be just due to the steering mechanism, or it might be designed in on purpose, depending upon the use of the vehicle.

Also, turning radii can change on a given vehicle when wheelbase changes.  So, a given model truck delivering concrete can change when used as a dumpster hauler, just to cite an example.

Check your variables, and design for the worst case.

cehall (Mechanical) (OP)
19 May 04 14:12
Thanks!  I will keep in mind the variables.  We might have to test drive (in the driveway) before we buy.

We will know how a semi does when they come for the oaks, cherry, and walnut to mill up.  We have to get around and skid drag them to crane on semi.  They may also be able to give some advise; before we lay the limestone and slag.

I would not look forward to moving the stone if we have problems.  But moving a garage or house would be much worse; so will make sure to test drive before the first foundation is finalized.
cehall (Mechanical) (OP)
25 May 04 8:57
I would once again thank everyone that posted to this.

We had a damaging storm come thru.  So, turn-around and driveway is natually wider.  Uprooted trees (7) and blow-down (cut 18-6"+).  We worked with two saws for four hours in three acres alone. Other 10 acres will just have to wait.
DwattedWabbit (Civil/Environmental)
9 Sep 04 16:23
Depending upon the local regulations, the length of the driveway, width, its use (private or public, one owner, or shared by two or more homeowners), etc., might require a turning radius or a hammerhead turnaround large enough to accommodate a fire engine/ladder truck.  Check with your local regulating agencies before you design and build.

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