SIDE ROAD INTERSECTION AND SUPERELEVATION 1

[evett]

What is the accepted procedure for dealing with the superelevation transition on a side road tying into a main line alignment when the main line profile is steep and the side road has a curve that produces a superelevation in the opposite direction? The intersection is a stop condition on the side road. Do you use full super on the side road curve and if so do you use the same rate of change that you used to get into the curve to also get out and match the adverse main line profile grade. The PT of the curve is close to the edge of pavement and there is not much room for transition. Is there a reference that covers this type situation out there? This situation is hard to describe so if you don’t understand I will be glad email you a sketch.

 

[gravel]

Looks like you have to apply some judgement with the blend-in. The super is for banking effects of a moving car. Approaching your stop sign, you have a situation where you don't need super, due to lower speed. Just because it is a curve, doesn't meean you have to super it,nor follow regulations exact. Just sorta start back at your PC and work towards the intersection to make the intersection blending work. Watch you don't get trapped water at the radius faces. Best to profile your actual curb returns, to check you don't have ponding. Try to make your approach paving mimic the crossing grade of main-line edge of pavement and even blend in your crown as a flat street by time your sideroad gets to the curb return area. Else, you will get a puddle on the upside (assuming you side street is coming downhill into the main). Adjust your new inlet locations accordingly, so any highside super doesn't spill over onto the travelway.

 

[ACtrafficengr]

Check if you can realign the sideroad to get a longer tangent on the sideroad before the intersection. It will give you more room for a transition, and improve the safety performance of the intersection.

Of coourse, depending on the existing crash history, and the cost of right of way, you may not be able to justify the expense.

 

[Maury]

You should get a copy of "Apolicy on Geometric Design Of Streets and Highways - 2001" published by AASHTO. It'll tell you the same thing that gravel and LTAPJim have said, in a little more detail. Realign the side road if you can, provide smooth transitions in a way that lets oncoming drivers see what is happening. Provide warning signs. Lighting is a good idea.