vertical alinement: help!

[longisland]

Hi,
Does anyone know how to design an uphill vertical alinement of three quarter mile long? the natural terrain is about 32 degrees. I'm thinking of 2 options
1) to introduce a climbing lane; the question is can I climb 3/4 mile at 9 degrees continuously?
2) alternatively, I'll stick with 500ft critical length at 9 degrees climb; what is the crest k required & what is the minimum length of the intermediate flat stretch between the 2 steep climbs?

Is there any writeup on the questions posted?

 

[roberttx]

Hi,

Here goes some thoughts about your questions. What you must check here, first is if your heaviest vehicle is going to be able to carry its load on such distance. You might want to compare it with figures on the AASHTO green book. Back in Mexico, what we use is that the reduction in speed is at most 15 mph on the climbing lane. Well, at least is a start. Then, the intermediate "stretch" between the two steep climbs is just for recovery, but you should use it in the same way just to know how much will the vehicle regain speed and into the last climb and how much lenght will be needed to recover.

As for the crest k, just check for the entering and exit slope and speed at that point. The table is there, too.

Good luck,
Roberto.

 

[trafficPro]

Dont forget downhill truck movements. trucks can lose brakes on steep downhills. Provide side of road escape runs, with level or uphill segments and a surface that can slow down truck, like deep, loose sand surface.