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Determining Pfd - Can Pfd be greater than 1.0?

Thanura Rabel
Opus International Consultants
Determining Pfd - Can Pfd be greater than 1.0? was posted on June 29th, 2017 at 10:30 PM EDT
regarding Chapter 13: Freeway Merge and Diverge Segments

Hi there,

I'm assessing the density of an off-ramp, with an upstream on-ramp approximately 115m away. Using Equation 13-10, I have determined PFD to be greater than 1.0.

Can Pfd be greater than 1.0 or does it only work 1.0 and below?

Thanks - appreciate any help.

Thanura

Scott Washburn
University of Florida
RE: Determining Pfd - Can Pfd be greater than 1.0? was posted on June 29th, 2017 at 10:55 PM EDT

1.0 is the maximum. If you send me your full set of inputs (swash@ce.ufl.edu), I can check your calculations and follow up with the HCQS committee as needed.

Bill Sampson
University of Florida
RE: Determining Pfd - Can Pfd be greater than 1.0? was posted on June 30th, 2017 at 7:14 AM EDT

Hi Thanura,

If the ratio of the upstream ramp flow rate to the length to the upstream ramp (vu/Lu) is greater than 0.2, you should revert to using Equation 13-9. This was a change to the HCM 2010 in June 2012.

Thanks, Bill

Thanura Rabel
Opus International Consultants
RE: Determining Pfd - Can Pfd be greater than 1.0? was posted on July 3rd, 2017 at 6:10 PM EDT

Thank you guys. I proceeded to use Eq 13-9

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