Traffic Volume Equations & Vehicle Types [AADT, K-factor, D-factor, PHF, Design Service Flow Rate]

AADT = Annual Average Daily Traffic (over 12 month period)
ADT = Average Daily Traffic (other time period)
DHV = Design Hour Volume (both directions)
DDHV = Directional Design Hour Volume (one direction)
DSFR = Design Service Flow Rate (peak 15-minutes in one direction)
K - Percent of traffic during the peak hour (typically 8% to 12%)
D - Proportion of traffic traveling in the predominant direction (typically 0.5 to 0.7)
PHF - Ratio of design hour volume to the peak 15-minute flow rate (typically 0.8 to 0.95)
The traffic growth rate equation (9:50) in this video is consistent with the "Single Payment Compound Amount" or "to F given P" in the engineering economics part of the reference handbook (Section 1.7, page 37). Not the traffic growth rate equations in section 5.5.9 of the reference handbook v1.1 (page 289), which are specific to pavement analysis calculations.
#TrafficEngineering #DanielFindley
0:00 Introduction
1:02 Design Vehicle Dimensions (Example: WB-40)
1:42 Traffic Volume Terminology
4:19 Basic Traffic Volume Equations
8:00 Peak Hour Factor Calculation
9:49 ADT Growth Rate
10:05 Example 3 - ADT Calculation
11:00 DHV Calculation
12:50 DSFR Calculation

[@hussain901]

Man thanks so much, you're a legend

[@FindleyDaniel]

You're welcome!

[@sundayojo7203]

Thanks so much sir. Example 4 - given 9,340 vehicles per day and to obtain vehicle per hour.

[@enp55]

Hi, thank you, very informative. Would you also suggest where I can find how to calculate/ estimate "traffic volume estimation in residential/neighborhood areas".

[@FindleyDaniel]

I think you're referring to trip generation, is that correct? The ITE Trip Generation Handbook is a great source for that (for instance, a single family home is expected to generate 9.44 trips per day).

[@bricegreco8292]

Given your comment in the description. Is example 3 still correct or expected on the PE exam?

[@FindleyDaniel]

Yes, I think this would still be a reasonable problem on the exam. To solve it, you should use the "Single Payment Compound Amount" or "to F given P" in the engineering economics part of the reference handbook (Section 1.7.10, page 42 of v1.2 - you'll find a value of 1.3439 for F/P with an n of 10). The traffic growth rate equations in section 5.5.9 of the reference handbook v1.1 (page 289), which are specific to pavement analysis calculations, were removed from v1.2 of the reference handbook.

[@falconly7095]

thank you Daniel
I really need to know how K is defined i mean how did they come out with these numbers 8-12 urban and 12-18 rural

[@FindleyDaniel]

Great question - technically, K is the 30th-highest hourly volume of the year. Because of the relatively higher volumes throughout the full day in urban areas compared to rural areas, urban areas typically have a lower K factor than rural areas. For instance, 10 PM in a rural area typically has very low traffic volumes (when I was growing up, in a rural location, only one business in my county was still open at that time), while an urban area typically has many businesses open and a much larger percentage of traffic still operating at that time.

[@leonardoz.wongbae9165]

Thanks so kindly, Sir. How do I use the AADT to design for pavement? Can I use the ADT to DEsign?

[@FindleyDaniel]

In most situations, you will not have an AADT value available. So, yes, ADT is appropriate and useful in most scenarios.

[@Jeff-lb2by]

I cant seem to locate the ADT adjusted equation, DHV equation, DDHV eqyuation, or DSFR equation in the greenook or the reference manual. Do you know where they are?

[@FindleyDaniel]

Unfortunately, all of these equations are not in the Greenbook or the Reference Handbook. However, v2.0.2 of the Reference Handbook has some content on pages 267-268 (section 5.1.3) and page 290 (section 5.5.7 and 5.5.8). Other volume related content is in textbooks and the Highway Capacity Manual.

[@oleopathic]

are these PE exam AM or PM (transpo)-level questions ? a mix, perhaphs?

[@FindleyDaniel]

I would consider this mostly AM topics, but I also believe some would be more PM-level.

[@richardnwachukwu234]

Informative

[@richardnwachukwu234]

I'm just remembering all these.
Being a polytechnic graduate gave me the opportunity to study these, but where can I practice these?

[@shrednoob5233]

is there any way to get adt from peak hour volume?

[@FindleyDaniel]

Yes, you can solve them in the reverse way. For instance, if you have the peak direction volume, you can divide it by K & D to get the ADT. If you have the combined directional volume, you can divide it by K to get the ADT.

[@shrednoob5233]

@@FindleyDaniel thanks for the response

[@sahanbaidya7778]

@@FindleyDaniel How to determine K & D? Can we assume as explained in this video? Or is there other better method to find them?

[@FindleyDaniel]

@@sahanbaidya7778 If you have local data (from the specific site or a similar one), that's the best. Otherwise, yes, it's usually ok to assume a K factor between 0.08 and 0.12 and a D factor 0.55 and 0.65. Or, something similar.

[@sahanbaidya7778]

@@FindleyDaniel sir, can you refer me any research paper or document to help me find K and D at my local area by observation at site? I would be extremely helpful.

[@oleopathic]

example #3. growth rate. ncees hb 1.1 has a similar eqn on page 289.
why are you using exponent "t" instead of ncees' "t-1"?
i understand that adt isn't the same as aadtt but still, the concept and the accompanying eqn ought to be same. no?

[@FindleyDaniel]

I'm going to look in the original reference material to see if/how they define "t". The common notation for this type of problem is for the number of years (not number of years minus 1). However, they may define time from the beginning of that time period, not the end. For example, there's a difference between the end of year 8 and the beginning of year 8. The traditional equation assumes the end of the year.

[@FindleyDaniel]

From my understanding, the traffic growth rate equations in section 5.5.9 of the reference handbook v1.1 (page 289), are specific to pavement analysis calculations. The traffic growth rate equation (9:50) in this video is consistent with the "Single Payment Compound Amount" or "to F given P" in the engineering economics part of the reference handbook (Section 1.7, page 37).

[@oleopathic]

audio volume too low.

[@oleopathic]

ncees hb 1.1, page 289 & others.