Guardrails and Sideslopes

[Althalus]

I've spent much of my career in site work. And it has been ages since I did municipal or transportation projects. So, I'm wondering if I have a faulty memory or if I'm remembering right.

I am in the process of writing new standards and design guides for my company. This is a guide for plant work. That means the speeds will be lower than highways. All the roads are ADT < 400.

I got to the subject of guardrails. One item that is considered a "hazard" is the sideslopes. i.e. the slope alone is the hazard, not a factor in determining the guardrail for some obstruction or other.

I had it in my head that if you have side-slopes of 5:1 or 6:1, that was considered flat enough that the slope itself is not necessarily a hazard, so no guardrail required. But someone just told me that we can go as steep as 3:1 without a guardrail.

I just tried visiting the DOT websites of four different states. And I can't find any reference to the sideslope (outside of the shoulder) being a hazard in and of itself. I do see it being a variable in determining the length of the guardrail, just not when there is no other hazard.

Anyone have some references?

 

[Pinwards]

I think that's covered in AASHTO's Roadside Design Guide - you might check there for more details.

#

 

[dik]

Can you tell us what their roadside design guide stipulates?

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[Pinwards]

I don't have a copy handy Dik, just recalled where the recommendations could be found from back in my (brief) stint in Transportation design. Good luck Althalus.

#

 

[dik]

Thanks... appreciated... maybe someone has this info... it would be good to know. I generally use 1:3 or 1:4, depending on the mood, but I'm unaware of a real reference.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik