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Posts Tagged ‘LOS’

You don’t hear about it much, but the Highway Capacity Manual does have a definition for pedestrian LOS:

Pedestrian LOS is determined based on the average delay per pedestrian (i.e., wait time). Pedestrian delay is calculated using two parameters: cycle length and effective green time for pedestrians. The HCM 2000 recommends estimating effective green time for pedestrians by taking the walk interval and adding 4 seconds of the flashing DON’T WALK interval to account for pedestrians who depart the curb after the start of flashing DON’T WALK. The equation for calculating pedestrian delay based on equation 18-5 of the HCM 2000:

The average pedestrian delay, in seconds, equals 0.5 times the square of the difference of cycle length minus effective green time for pedestrians, both in seconds, all divided by the cycle length.
Where: dp = average pedestrian delay (s)
C = cycle length (s)
g = effective green time for pedestrians (s)

Pedestrian LOS thresholds at signalized intersections.

LOS

Pedestrian Delay (sec/ped)

Likelihood of Noncompliance

A

< 10

Low

B

≥ 10-20

 

C

> 20-30

Moderate

D

> 30-40

 

E

> 40-60

High

F

> 60

Very High

Using this metric, one can predict the amount of jaywalking. Intersections with “A” or “B” pedestrian LOS will have a high degree of compliance. Intersections with “C” or “D” LOS will have a moderate amount of jaywalking. Intersections with “E” or “F” LOS, well, can expect to have lots of jaywalking.

Because I don’t have a social life, I spent the better part of last evening with a stopwatch timing the signalized intersections and observing pedestrians in my Berkeley neighborhood. Supposedly, this is a pedestrian-friendly city and yet pedestrian LOS were all within the “C” and “D” range — meaning one can expect a moderate amount of noncompliance. Jaywalking is fairly common, so the pedestrian LOS chart models reality pretty well.

As in most cities, the pedestrian signals in my neighborhood were upgraded to the beg-button type. Pedestrians must press a button, then wait (as long as a full cycle) to get the walk light. What if instead these beg-buttons were Pedestrian Priority buttons? The walk light would come much sooner, and LOS would move into the A” or “B” range. There would be less jaywalking, and a much improved pedestrian experience.

claremont

The Claremont/62nd intersection has pedestrian LOS of “E”. Everyone jaywalks here.

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Grade Inflation

LOS (Level of Service) is one of the most misunderstood metrics of traffic analysis.

The term is familiar to anyone who has read an EIR. LOS assigns a “grade” for intersection performance. The grades run from “A” to “F”, with “A” being most free-flowing, and “F” having the most delay.

The first misunderstanding  is that LOS measures vehicles, not people. So a delay to a bus with 40 passengers counts the same as an SOV. Most environmentalists are aware of this issue, and some localities try to compensate for this.

The second misunderstanding is that LOS only measures delay during the “peak-of-the-peak” (usually just the busiest 15 minutes of the day). Many people will see a bad grade and not understand that it only applies to a small portion of the day.

But the really big misunderstanding is that LOS “A” is not the best grade. LOS “A” means the road is overbuilt. In other words, taxpayers wasted money on the roadway. The best grade is actually around “C”. Intersections with LOS “C” still perform pretty darn well during peak hours, and very well the rest of the day.

LOS "A"

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