Commercial driveway connection to locad road

[Froachie]

What is the proper way to grade a t-intersection?

I have a site where my proposed driveway/entrance connects to an existing road at a max of 5% grade. However, the local road I need to connect to has a longitudinal slope of 6%.

Can anyone lead me to a detail or drawing of how to grade this type of connection, where my driveway/entrance will be connecting to a road that is not level?

My driveway is running north to south and the road I need to connect to is running west to east at a slope of 5%

 

[Ron]

Start at the road slope. Meet that on both sides, so now your driveway, at the entrance, has a 5% cross slope. Transition to your necessary point of level grade (say, your garage entrance). Draw a straight line from each point at the roadway to each point at the garage. That's it, unless you want a 5ft or so level apron off your garage. That will just make you driveway slope steeper.

 

[Froachie]

Ok I probably should be a bit clearer, as when I reread my question, I confused myself.

I have a site where the entrance is at elevation 840. The road I need to connect my entrance to is at elevation 843 and its south of the site. Starting at my site, I go north and I run 2% then I increase to 5% and then as I approach the local road I am connecting to, I decrease to 2% over 15 ft.

The question I have is that the local road I am connecting to, has a longitudinal slope of 6% running west to east, which would make my driveway have a 6% cross slope at the point where my driveway meets the local road edge of pavement. Is this ok? Is 5% monoslope (west to east) on my driveway acceptable? I could transition to a crown in the driveway, however I think that the 15 ft of 2% roadway will need to be increased otherwise there is going to be like a 10% hump from the local road to the driveway before it starts descending to my site at 5%.

The driveway is 40' wide and will connect a commercial site to the local road.

 

[Ron]

The only constraints are ground clearance of the vehicles traversing the driveway and drainage considerations from the road to your entry, since you are lower than the roadway.

 

[brandoncdg]

Don't make larger than 12% grade breaks is the first thing. When you warp the driveway make sure of that. You should make sure to get the standard driveway templates for the city/county you are working in.

We just tried using an APWA standard to get around a city standard and the city engineer forced us to figure out how to get the city driveway standard working. This almost killed a mixed-use project for us.

Also after designing the driveway call over to the city engineer or inspector and ask if they have any issues with your design. Of course be ready to have a highlighted print to fax.

Civil Development Group, LLC
Los Angeles Civil Engineering specializing in Hillside Grading

http://www.civildevelopmentgroup.com

http://www.civildevelopmentgroup.com/blog

 

[beej67]

This thread needs sketches.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[Froachie]

I attached a quick sketch. I am wondering how I need to warp the grading to produce an acceptable cross slope of the driveway at the tie in with the edge of pavement of the local rd. I need to warp from 5% to 2%? Or is 5% ok for the cross slope of the driveway where it meets the local rd.

The driveway will have 2 lanes of traffic. I think its proposed for approximately 36 or so feet wide at the moment

 

[hmcrae]

If the road is already there, you have no choice but to meet its longitudinal slope of 5% with a cross slope of 5%. Figure your math off the driveway centerline (839.7 to 842.5) intersecting the edge of the local road. The warp will be determined by rolling the road from the 5% slope to meet the slope of the parking lot. You will have two edges of pavement (left and right) which will run at different slopes. Use those grades to control everything and all interior spot grades can be interpolated. As steep as you are, puddles will not be your problem. check for potential high centering (and if you have a good reference for that, please share it, as I have never really found anything useful for that).