6 min solution - Transp depth- problem 27

[Predgw]

Problem ask for saturation flow rate in a 4 way intersection. Pretty straightforward execpt the new 2010 HCM makes things interesting.

Looks like the formula in the 2010 HCM has changed for lane width adjustment. Exh. 18-13 gives an adjustment factor for lane width fw of 1.0 for lanes between 10.0' and 12.9' wide. From my reference books that all used the 2000 HCM, the lane width adjustment was calculated using 1+(w-12/12). This changes the answer and caused me to get the problem wrong.

I used the formula starting on page 18-35 in the 2010 HCM. One number I can't find is the base saturation flow rate. All my reference manuals use 1900pcphpl for this. I can not find this in the 2010 HCM to verify. Anybody know where this is shown? This is a heads up for you all, or the chance to let me know I'm using the wrong formula.

Thanks

 

[BrettL0726]

I do not have access to the exact problem you are asking about, but I can help you with the base saturation flow rate. You'll find it in the default values table, Exhibit 18-28 in the 2010 HCM. It is in fact 1900 pcphpl (or 1750 if not a metropolitan area). It also seems you are getting the lane width factor correctly- the table is pretty straight forward.

 

[Predgw]

Awesome. Thanks This change in reference has been alot of work as I need to verify reference material that used the 2000 HCM. Of course the page numbers, chapters and exhibits do not match up.

Thanks again