Passing sight distance - land desktop '04

[ACtrafficengr]

I know that LD will calculate passing sight distance for crest vertical curves, but is there a way to find the locations where available passing sight distance falls below the minimum required for a passing zone in the MUTCD?

Thanks!

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[chicopee]

I pulled out my 1959 Route Surveys and Design by T.F. Hickerson. On paragraph 118 (pg 216) shows the relationships between sight distance (S), length of vertical curve (L) and eccentricity (e). There are two cases presented with S<L and L>S. You may want to check this reference or a more recent one out to see if this is what you are looking for.
What do the initil MUTCD stand for?

 

[ACtrafficengr]

Sorry - MUTCD = Manual on Uniform Traffic Control Devices, the US standard on signs, pavement markings, signals, etc.

None of the references I have or can find on-line have the eccentricity term. Would you mind posting the equations here?

It's hard to believe I have to go back to a book seven years older than I am to find this! We have some old blueprints downstairs that show the sight distance at 50' intervals. I wonder why the practice fell out of use.

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[chicopee]

Better yet, I have made six .jpg pictures of the material.
Let me have your Email address so that as I'll be able to send them to you. There are too many derivations to post any one formula and it would help understanding the limitation of the formulae.
The free file sharing can only accept one picture at a time. It will not let me attach the six .jpg pictures.

 

[CarlB]

How about this no cad/no formula approach: Lay a straight edge on the profile, one end at the driver location, 3.5' above finish grade (or whatever the eye height is now), tangent with the FG, and intersecting 0.5' above ground (or other object height). Distance from driver to ground intersection is the passing sight distance.

 

[chicopee]

Not exactly. Must consider heights of drivers on both sides of the hill.
let S=linear distance between drivers
L=linear distance between P.O.T.'s on both sides of hill
h1,h2= heights of driver on both sides of hill; however heights are parallel to eccentricity "e" and not vetical if parabolic vertical curve is asymetrical
e=AL/800
whereby A=algebraic difference in grades,percent
e=parallel to Y axis of parabola however its position can be anywhere on the curve not necessarily at point of origin. "e" will also intersect the point of vertical intersection created by two tangent lines (PC and PT) on both sides of hill.

case 1 : S<L
L= (S^2 * A)/ (100 * ((2h1)^.5 + (2h2)^.5)^2)

case 2 : S>L
L= 2S - (200 * ((h1)^.5 + (h2)^.5)^2) / A