Pedestrian min. green time (LOS)

[305Gurl]

If pedestrian volume are given for a north and a south approach for a particular road, where the volume is 10 peds/cycle in the NB direction and 30 peds/cycle in the SB approach. The way how the minimum pedestrian green time is found is NOT to sum both approaces first, but to use the higher volume (30 peds/cycle) since this will govern. This makes sense, as the lager green time would cover the smaller green time. This caught me off surprise over the weekend, where I worked a problem but I added the NB and the SB peds volume and came up with the incorrect answer for the minimum green time.

Just to feel safe for the exam....This is the approach to use, correct?

 

[ptatohed]

If pedestrian volume are given for a north and a south approach for a particular road, where the volume is 10 peds/cycle in the NB direction and 30 peds/cycle in the SB approach. The way how the minimum pedestrian green time is found is NOT to sum both approaces first, but to use the higher volume (30 peds/cycle) since this will govern. This makes sense, as the lager green time would cover the smaller green time. This caught me off surprise over the weekend, where I worked a problem but I added the NB and the SB peds volume and came up with the incorrect answer for the minimum green time.

Just to feel safe for the exam....This is the approach to use, correct?

305, I could be wrong but I thought the effective green time required for pedestrian crossing at a crosswalk included all pedestrians in the crosswalk during a given cycle (both directions). Please see page 18-12 of the HCM2000. To calculate t (total crossing time, eqn 18-13), you need to calculate Nped (# of peds crossing during an interval, eqn 18-12) which is Nped = v(C-G)/C and v is pedestrian volume on the subject walkway (i.e. both directions). That's my take. Anyone else?

 

[rejectedbytexas]

Nice discussion here! I am not a PE yet but have conducted doctoral research on pedestrians.

I may be incorrect, but In my opinion, the total volume of 40 ped/cycle can be more suitable.

If you check HCM 2000 or Traffic Engineering by Roess, Nped = number of pedestrians crossing during an interval, Nped is calculated based on v = pedestrian volume on the subject walkway. None of these parameters is direction-specific.

If you check HCM 2010, you will see things changed a lot. The new HCM differentiate opposing ped flow (denoted as di and do), and then "sum up" the seperatedly calculated t_p into a so-called "crosswalk occupancy time".

My understanding is HCM 2010's equations are good but not designed for signal timing purposes. I will stick to the textbook by Roess, which explictly states HCM 2000 equation can be used for signal timing purposes. If I encounter this problem in real world, I will consider longer ped green for senior citizens...

Sammy

 

[Peele1]

Nice discussion here! I am not a PE yet but have conducted doctoral research on pedestrians.

I may be incorrect, but In my opinion, the total volume of 40 ped/cycle can be more suitable.

If you check HCM 2000 or Traffic Engineering by Roess, Nped = number of pedestrians crossing during an interval, Nped is calculated based on v = pedestrian volume on the subject walkway. None of these parameters is direction-specific.

If you check HCM 2010, you will see things changed a lot. The new HCM differentiate opposing ped flow (denoted as di and do), and then "sum up" the seperatedly calculated t_p into a so-called "crosswalk occupancy time".

My understanding is HCM 2010's equations are good but not designed for signal timing purposes. I will stick to the textbook by Roess, which explictly states HCM 2000 equation can be used for signal timing purposes. If I encounter this problem in real world, I will consider longer ped green for senior citizens...

Sammy

Yes, in the real world, please consider longer crossing times for seniors, wheelchairs, strollers, kids, etc. especially on wider roads and/or higher speed roads.

If a senior gets 1/2 way across a two lane road, it's not a big problem, but if they get 1/2 way across a 6 lane road, it may be a huge problem. Does HCM or anything take the total width into consideration?

 

[ptatohed]

Thanks for the info regarding the 2010 HCM Sammy. I haven't yet "familiarized myself" with the 2010. Ironically, I just got my first copy of the 2010 HCM this morning.

Peele, the width should be built into the timing calculation since time = distance / speed. Wether you're using an Sp of 3.3 ft/s or 4.0 ft/s, the TS accounts for the length of crosswalk Ld. See Chapt 18 of the 2010 HCM.

 

[rejectedbytexas]

Thanks for the info regarding the 2010 HCM Sammy. I haven't yet "familiarized myself" with the 2010. Ironically, I just got my first copy of the 2010 HCM this morning.

Peele, the width should be built into the timing calculation since time = distance / speed. Wether you're using an Sp of 3.3 ft/s or 4.0 ft/s, the TS accounts for the length of crosswalk Ld. See Chapt 18 of the 2010 HCM.

HCM 2010 is not well organized for whom are familiar with HCM 2000. A headache now is: should I bring 2010 or 2000 version to the upcoming October exam? All the current CERM and NCEES sample questions are based on HCM 2000....

Caught by the transitions of HCM and AASHTO Greenbook.

 

[rejectedbytexas]

Peele, I totally agree. I think the flexibility we may control is about what walking speed to be used in the HCM equations. There has been a debate on decreasing the design walking speed for a while.

For a street that is too wide, given you have a wide, raised median as refuge, we can consider using two sets of signals to control pedestrians. One signal for from curb to median, the other signal for from the median to the other curb. Then we can use overlaps for pedestrians. I used to live in Beijing and ever see a ten-lane arterial road :beat: controlled that way. In US, we only see that kind of ped facility on frontage road.