Superelevation

[ghim]

Trying to solve this super elevation problems. But I don't know how to get the number of lanes rotated. (For the length of tangent runout and length of superelevation, see GDHS 3-25/3-26.)

Anybody knows?

Thanks in adavnce....

superelevation.pdf

 

[ptatohed]

Trying to solve this super elevation problems. But I don't know how to get the number of lanes rotated. (For the length of tangent runout and length of superelevation, see GDHS 3-25/3-26.)
Anybody knows?

Thanks in adavnce....

ghim,

Please look at AASHTO GDHS (2004) page 178, Exh 3-31. It has a pretty clear depiction of n<sub>1 (Number of lanes rotated). Basically, it's usually half your typical street section (the half on the other side of the CL which will be rotated from a regular crowned section with a negative slope to a superelevated section with a positive slope). Ex. a 2-lane road (one lane on each side of the CL) will have an n1 = 1, a 4-lane road will have an n1 = 2, a 6-lane road will have an n1 = 2, etc. I hope that helps.

 

[ghim]

Trying to solve this super elevation problems. But I don't know how to get the number of lanes rotated. (For the length of tangent runout and length of superelevation, see GDHS 3-25/3-26.)
Anybody knows?

Thanks in adavnce....

ghim,

Please look at AASHTO GDHS (2004) page 178, Exh 3-31. It has a pretty clear depiction of n<sub>1 (Number of lanes rotated). Basically, it's usually half your typical street section (the half on the other side of the CL which will be rotated from a regular crowned section with a negative slope to a superelevated section with a positive slope). Ex. a 2-lane road (one lane on each side of the CL) will have an n1 = 1, a 4-lane road will have an n1 = 2, a 6-lane road will have an n1 = 2, etc. I hope that helps.

Thank you for your quick response, ptatohed.

However, in the solution for this problem, it says, n1=2.5 instead of 2. Is this correct? I thought n1=2 though.

Also, in your answer, a 6-lane road will have an n1=3? or 2? I thought it is 3. I might be wrong......

 

[ptatohed]

Trying to solve this super elevation problems. But I don't know how to get the number of lanes rotated. (For the length of tangent runout and length of superelevation, see GDHS 3-25/3-26.)
Anybody knows?

Thanks in adavnce....

ghim,

Please look at AASHTO GDHS (2004) page 178, Exh 3-31. It has a pretty clear depiction of n<sub>1 (Number of lanes rotated). Basically, it's usually half your typical street section (the half on the other side of the CL which will be rotated from a regular crowned section with a negative slope to a superelevated section with a positive slope). Ex. a 2-lane road (one lane on each side of the CL) will have an n1 = 1, a 4-lane road will have an n1 = 2, a 6-lane road will have an n1 = 2, etc. I hope that helps.

Thank you for your quick response, ptatohed.

However, in the solution for this problem, it says, n1=2.5 instead of 2. Is this correct? I thought n1=2 though.

Also, in your answer, a 6-lane road will have an n1=3? or 2? I thought it is 3. I might be wrong......

ghim,

Yes, sorry about my typo, I meant to say that a 6-lane road would have an n1 = 3.

In your specific problem example, the typical section is a 4-lane road but there is also a dedicated left turn lane, which is considered a 5th lane. So, they are coming up with n1 = 2.5 by dividing 5 in half. The CL/crown must be located in the center of the center left turn (or "suicide") lane. Does that make sense?

 

[ghim]

Trying to solve this super elevation problems. But I don't know how to get the number of lanes rotated. (For the length of tangent runout and length of superelevation, see GDHS 3-25/3-26.)
Anybody knows?

Thanks in adavnce....

ghim,

Please look at AASHTO GDHS (2004) page 178, Exh 3-31. It has a pretty clear depiction of n<sub>1 (Number of lanes rotated). Basically, it's usually half your typical street section (the half on the other side of the CL which will be rotated from a regular crowned section with a negative slope to a superelevated section with a positive slope). Ex. a 2-lane road (one lane on each side of the CL) will have an n1 = 1, a 4-lane road will have an n1 = 2, a 6-lane road will have an n1 = 2, etc. I hope that helps.

Thank you for your quick response, ptatohed.

However, in the solution for this problem, it says, n1=2.5 instead of 2. Is this correct? I thought n1=2 though.

Also, in your answer, a 6-lane road will have an n1=3? or 2? I thought it is 3. I might be wrong......

ghim,

Yes, sorry about my typo, I meant to say that a 6-lane road would have an n1 = 3.

In your specific problem example, the typical section is a 4-lane road but there is also a dedicated left turn lane, which is considered a 5th lane. So, they are coming up with n1 = 2.5 by dividing 5 in half. The CL/crown must be located in the center of the center left turn (or "suicide") lane. Does that make sense?

Thank you, ptatohed. I got it now.