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Freeway Weaving - Weaving Length Threshold

Kevin Mascarina
Freeway Weaving - Weaving Length Threshold was posted on January 25th, 2017 at 6:25 AM EST
regarding Chapter 12: Freeway Weaving Segments

I found an external reference which suggests that the maximum weaving segment length is limited to 2,500ft in the HCM2010. Exceeding this value the segment will need to be analyzed as separate ramps. Can anyone confirm if such a value is found in the HCM2010?

If I am correct, the HCM2010 does not suggest any value. It does provide a methodology for the computation of the max weaving length (Lmax) and is compared against the weaving segment length (Ls). If Ls >= Lmax then it should be analyzed as separate ramps.

(Edited January 25th, 2017 at 6:53 AM EST)
Bill Sampson
University of Florida
RE: Freeway Weaving - Weaving Length Threshold was posted on January 25th, 2017 at 7:52 AM EST

From the HCM: If the segment is too long to be considered a weaving segment, then the merge and diverge areas are treated separately. In these cases, Chapter 14 (Merge & Diverge) performs ramp capacity checks for those segments; however, merge and diverge segments with a continuous lane add or lane drop are eventually analyzed operationally as a basic freeway segment using the procedures in Chapter 12 (Basic). An distance falling outside the influence areas of the merge and diverge segments would be considered to be a basic freeway segment and analyzed accordingly. Hope this helps.

(Edited January 25th, 2017 at 7:53 AM EST)
Paul Ryus
Kittelson & Associates, Inc.
RE: Freeway Weaving - Weaving Length Threshold was posted on January 25th, 2017 at 8:08 AM EST

Regarding the maximum weaving length question, you are correct--in the HCM 2010, the maximum weaving segment length is not a fixed value, but depends on the weaving volume ratio and the number of weaving lanes, and is calculated with Equation 12-4 (page 12-15). In the HCM 2000 method, the maximum weaving segment length was fixed at 2,500 feet (HCM 2000, bottom of page 24-9).

Kevin Mascarina
RE: Freeway Weaving - Weaving Length Threshold was posted on January 25th, 2017 at 9:05 AM EST

Thanks Bill and Paul!

(update)

Indeed if Ls >= Lmax then the segment will be treated as a basic freeway segment as stated in page 10-23 (replacement pages dated Jan 12-Feb 13). If this is the case, shouldn't the statements in page 12-16 just below Exhibit 12-9 be corrected accordingly from "If the segment is too long to be considered a weaving segment, then the merge and diverge areas are treated separately" to "If the segment is too long to be considered a weaving segment, then the segment is treated as a basic freeway segment". There would be no need to check Lmax if there was no continuous lane between the merge and diverge points.

(Edited January 25th, 2017 at 2:34 PM EST)

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