Space Mean Speed

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winner9459

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I know the formula for calculating Space mean speed is pretty straight forward, but I am getting confused by the calculation shown in HCM.

If you look at page 7-3 in the end the SMS is supposed to be 38.298, I cannot understand how HCM has arrived at 25.5 mi/h.

I used nL/ (sum of travel times); n is the no. measurements, L is the distance. Can some one please review this for me.

Thanks.

 
I know the formula for calculating Space mean speed is pretty straight forward, but I am getting confused by the calculation shown in HCM.
If you look at page 7-3 in the end the SMS is supposed to be 38.298, I cannot understand how HCM has arrived at 25.5 mi/h.

I used nL/ (sum of travel times); n is the no. measurements, L is the distance. Can some one please review this for me.

Thanks.
Where in the HCM do you see the example? I see the formula at the end of page 7-3, but don't see a numerical example. I'm looking at HCM 2000

 
Probably this text would help you locate it.

"It is possible to calculate both time mean and space mean speeds from a sample of

individual vehicle speeds. For example, three vehicles are recorded with speeds of 30,

40, and 50 mi/h. The time to traverse 1 mi is 2.0 min, 1.5 min, and 1.2 min, respectively.

The time mean speed is 40 mi/h, calculated as (30 + 40 + 50)/3. The space mean speed is

38.3 mi/h, calculated as (60)[3 ÷ (2.0 + 1.5 + 1.2)]."

Thanks.

I know the formula for calculating Space mean speed is pretty straight forward, but I am getting confused by the calculation shown in HCM.
If you look at page 7-3 in the end the SMS is supposed to be 38.298, I cannot understand how HCM has arrived at 25.5 mi/h.

I used nL/ (sum of travel times); n is the no. measurements, L is the distance. Can some one please review this for me.

Thanks.
Where in the HCM do you see the example? I see the formula at the end of page 7-3, but don't see a numerical example. I'm looking at HCM 2000
 
But, the text you extracted shows the SMS calculated as 38.3 (correct answer). Where is the 25.5 you are referring to?

 
that's interesting, the hard copy I am referring to has the wrong answer which made me go hmmmmm.....The text I posted is from the soft copy of HCM I have. Probably they updated it with the corrections.

Thanks for the help.

 
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