2012 Georgia Traffic Monitoring Program

2012 Georgia Traffic Monitoring Program
Photo By: Paul Brennan
Office of Transportation Data
Facilitator: Jane Smith, State Transportation Data Administrator Prepared By: Kiisa Wiegand, Business Analyst Original Draft Date: 4/5/2012 Date of Last Revision: 6/27/2012

Georgia DOT

Office of Transportation Data

TABLE OF CONTENTS

I.

PURPOSE .......................................................................................................................................... 2

II. BACKGROUND.................................................................................................................................. 2

III. TRAFFIC DATA COLLECTION PROGRAM OVERVIEW ........................................................................ 3

IV. TRAFFIC DATA COLLECTION ............................................................................................................. 4

V. CONTINUOUS MONITORING PROGRAM ......................................................................................... 6

Selection Criteria for Installation of a New ATR Site ....................................................................... 8

VI. SHORT-TERM MONITORING PROGRAM .......................................................................................... 9

VII. WEIGH-IN-MOTION PROGRAM...................................................................................................... 11

VIII. QUALITY CONTROL AND ASSURANCE............................................................................................ 12

IX. WEEKLY DATA PROCESSING........................................................................................................... 13

Weekly Data Processing for Continuous Monitoring Sites ............................................................ 13

Weekly Data Processing for Short-Term Monitoring Sites ............................................................ 15

X. ANNUAL DATA PROCESSING.......................................................................................................... 18

Management of Traffic Count Segments....................................................................................... 19

Calculation of Traffic on High Volume Roads (Step Down Method).............................................. 20

Traffic Count Collection and Estimation on Local Roads ............................................................... 21

Traffic Adjustment Factors............................................................................................................. 22

XI. OTHER CONSIDERATIONS .............................................................................................................. 25

REFERENCES................................................................................................................................................ 26

Appendix A: FHWA 13-Bin Vehicle Classification Scheme .......................................................................... 27

Appendix B: 2011 and 2012 Portable Traffic Collections............................................................................ 28

Appendix C: Georgia Counties and FIPS Identification Numbers ............................................................... 29

Appendix D: Traffic Calculations ................................................................................................................. 30

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I. PURPOSE
Federal Regulations 23 CFR 500.202 states, "Traffic monitoring system means a systematic process for the collection, analysis, summary, and retention of highway and transit related person and vehicular traffic data." Federal Regulations 23 CFR 500.203 mandates, "Each state shall develop, establish, and implement, on a continuing basis, a TMS to be used for obtaining highway traffic data..." This document is intended to record the current procedures and practices of the Georgia Department of Transportation's traffic monitoring system.
This document will provide a comprehensive analysis that will fulfill the Federal regulation stated above. The study of traffic data procedures and monitoring is an extensive and very detailed subject with numerous publications and publicly available documentation. The focus of the subject of this document will be constrained to specifics on the Office of Transportation Data's management of the traffic data collection program, as currently performed, including collecting traffic data; quality control and assurance; weekly and annual data processing; and other considerations.

II. BACKGROUND
The Federal Highway Administration (FHWA) requires every state to submit an annual Highway Performance Monitoring System (HPMS) report containing traffic count data, physical characteristics and other pertinent road data. This submittal is used in legislation, and to determine state funding of highway and road projects. According to the HPMS Field Manual, "State Maintenance of a comprehensive traffic monitoring data program to provide quality, timely, and complete traffic volume and vehicle classification data is important for meeting HPMS requirements." This report serves as a primary component for determining the Federal transportation funding apportionment allocated to states.
The data that the Office of Transportation Data (OTD) collects is used for many reasons by internal departments, including the Office of Planning, the Office of Bridge Design and the Office of Materials and Research. Traffic counts are used to determine traffic patterns and flows for modeling purposes. They are also used to alleviate congestion with the construction of new routes or alternate designs. The Office of Bridge Design uses Annual Average Daily Traffic (AADT) data to determine the Bridge Sufficiency Rating. One other example, the Office of Materials Research uses a combination of truck percentages and AADT data to develop factors that assess the deterioration of pavement. The Traffic Operations Office uses the volume data for safety related purposes (e.g., calculating crash rates and addressing safety issues).
OTD provides data to a large variety of external customers. Customers of the data include transportation planning professionals, educational institutions, design engineers, contractors, real estate agencies, private companies, and other government agencies. Traffic data is important in determining which routes citizens are using for their daily commutes and leisure travel. During emergency evacuations in inclement weather, critical traffic data is provided to the Georgia Emergency Management Agency and surrounding states. The data is used on both a state and national level by the U.S. Department of Transportation and other customers for planning, modeling, allocation of funding, informational purposes, etc.

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III. TRAFFIC DATA COLLECTION PROGRAM OVERVIEW
The Georgia Department of Transportation's Office of Transportation Data has an extensive, quality driven traffic count program in compliance with all Federal regulations and guidelines. Branches within OTD work together on the traffic monitoring program. The Traffic Data Collection Branch collects traffic count data using portable collection devices, or permanent collection devices. Physical road characteristics are also collected on an ongoing basis by Road Inventory Crews managed by the Road Data Collection Branch. All incoming data is processed with defined and established quality assurance and control measures by the Data Reporting and Quality Control Branch. The Geospatial Information System (GIS) Branch provides digital map analysis of traffic count data, including verification of traffic count placement, and maps that the traffic collectors use as guides.
FHWA requires that all states collect traffic data on the Federal-aid system and provide Vehicle Miles Traveled (VMT) estimates for the local functional classification (FC) systems as directed by Federal regulations. The traffic collection program is designed to provide statistically valid data for the HPMS report which is also required by FHWA on an annual basis. The design of the program closely follows the guidelines of the Traffic Monitoring Guide (TMG). The following is a list of the road systems included in the traffic collection program:
US Routes State Routes County Roads City Streets Ramps
OTD has created a Traffic Data Collection Guide which details portable data collection standards, county coverage, collecting vehicle classification data, collecting GPS coordinate data, set-up of portable traffic monitoring stations (PTMS), collecting turning movements, etc.
Georgia's State Traffic and Reporting Statistics (STARS) provides AADT counts collected from permanent and portable traffic collection devices throughout the state for every segment of Georgia's State Highway System. The traffic count data is updated on this website annually: http://www.dot.ga.gov/statistics/stars/Pages/default.aspx.
Georgia's Transportation Polling and Analysis System (TPAS) provides traffic data collected 24 hours per day, seven days per week, 365 days per year from permanent traffic collection devices throughout the state for Georgia's State Highway System. Georgia's TPAS is intended for the general public to view current traffic information and historical traffic information dating back to January 1, 2008. The traffic data is updated on this website daily: http://www.dot.ga.gov/statistics/trafficdata/pages/tpas.aspx.
Also, Automatic Traffic Recorder (ATR) Traffic Data Reports are published by OTD annually and contain information such as truck percentages by location, vehicle classification by functional classification and hour, and maps for locating ATR sites. The annual reports can be viewed on the following website: http://www.dot.ga.gov/statistics/TrafficData/Pages/atr.aspx.

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IV. TRAFFIC DATA COLLECTION
The foundation of the traffic monitoring program is the collection of traffic data. Data can be collected using continuous counters, portable traffic monitoring system sites, short-term counts, or portable and continuous weigh-in-motion sites. Specific sites and types of traffic data collection can be requested by internal GDOT offices. Other potential future sources of traffic data include Intelligent Transportation System (ITS) data and data sharing.
Continuous Counts As of April 2012, OTD has 234 operational, permanent Automatic Traffic Recorder (ATR) sites located on road systems throughout the state. These sites are operational 24 hours per day, seven days per week, 365 days per year excluding any necessary maintenance periods. Permanent sites are polled on a daily basis. Vehicle classification data, traffic volume, and traffic speed is collected. Vehicle classification can also be referred to as classification or class data.
Portable Traffic Monitoring System (PTMS) The Portable Traffic Monitoring System (PTMS) is a seasonally collected ATR site that does not have either a cellular or a land line connection. A field technician drives to the PTMS site and physically connects a portable traffic loop counter to the site. Traffic data is typically collected for a forty-eight hour period every three months.
Short-Term Counts Portable collection devices are pneumatic tube(s) that are stretched across a road and secured on both sides by a field technician. They are connected to a counter on one side of the road and the data is usually collected for a 48-hour period. The devices can be programmed to collect vehicle classification counts as well as volume counts. OTD collects short-term volume counts at approximately 8,000 locations statewide annually.
Portable and Continuous Weigh-In-Motion (WIM) Portable and permanent Weigh-In-Motion (WIM) sensors and the related data collection equipment are utilized to collect truck weight data statewide at Strategic Highway Research Program (SHRP) and HPMS sites. There are about 90 sites located throughout Georgia at which the WIM data is collected on a cyclical basis; approximately 30 sites each year on a three year cycle. Additionally, OTD has two permanent WIM sites that collect data 24 hours per day, seven days per week, 365 days per year excluding any necessary maintenance periods.
Special Requests Specifically requested traffic data or special requests are collected at site specific and project specific locations statewide. Primarily, special requests are requested by the Office of Environment and Location, the Office of Planning, and the Districts' Traffic Operations for project specific studies, which may include short-term vehicle classification, volume counts or turning movements at an intersection. Some of the special requests for traffic are event driven. For example, OTD usually gets a request to provide traffic volume counts when there is a race at the Atlanta Motor Speedway.
ITS and Data Sharing The FHWA has encouraged all states to invest in innovative collection practices, such as data sharing or use of Intelligent Transportation System (ITS) data. Through the years, OTD has been actively seeking

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methods to augment traffic collection through partnerships. From 2006 to the present, OTD participated in a series of meetings with Information Technology Outreach Services (ITOS) a part of the University of Georgia's Carl Vincent Institute of Government, and local governments in attempts to collaborate on equipment and quality control standards in order to integrate traffic data. As of April 2012, eight counties have a traffic collection program and are interested in a data sharing agreement.
The ITS or Video Detection System (VDS) data, which is primarily focused on high volume Interstates in metropolitan areas, provides a limited coverage of the traffic monitoring program. In 2011, OTD did a comparison study of ATR data and GDOT's Traffic Management Center's VDS data at several locations around Atlanta and discovered that the AADT volumes varied from 10-50%. This is not adequate for AADT and VMT calculations, and reporting purposes. For future use, defined data quality standards and goals, an examination of the calibration methods, and additional field testing would need to occur for OTD to use the VDS data.

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V. CONTINUOUS MONITORING PROGRAM

Continuous monitoring sites or otherwise known as Automatic Traffic Recorder (ATR) sites are installed on all types of roadways (State Routes, County Roads, and City Streets) in both asphalt and concrete. OTD's ATR sites provide volume, speed, and vehicle classification. These sites are continuously operational (24 hours per day, seven days per week, 365 days per year) except during any necessary maintenance periods. The data is stored on site in an ATR Controller Cabinet, prior to being automatically polled every night through the use of land line or cellular modems located at each ATR site.

ATR Controller Cabinet

In Georgia, all ATR sites have equipment configurations that are capable of collecting vehicle classification in addition to volume counts. The ATR sites utilize two Inductive Loop Sensors and one Class II Piezoelectric Sensor embedded in each lane that operates according to the manufacturer's specifications. The system may require one of more of the following items as part of the system: Controller Cabinet with Back Plane Plates, lightning suppressors, pull boxes, conduits, grounding electrodes, poles, concrete aprons, batteries and a solar panel. The piezoelectric sensors, equipment cabinet, inductive loops, cables, leads, and electronic hardware and software are furnished, installed, tested, calibrated and made ready for operation by OTD's contractor. Stringent adherence to calibration and set-up routines for equipment are required to ensure a high level of traffic data accuracy.

ATR Installed in Pavement

Inductive Loop

Piezoelectric Sensor

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Georgia DOT Georgia ATR Site Locations
ATR sites provide valuable data statistics, such as:
AADT, vehicle classification, and truck percentages
Daily, monthly, and axle adjustment factors by traffic pattern group
Design hour factors (peak hour and 30th highest hour) used for the design of highways
Traffic growth and patterns Accurate traffic volume data
used to calculate high volume Interstate and other freeway traffic (Step Down Method)
2012 Geogia Traffic Monitoring Program

Office of Transportation Data As of April 2012, OTD has 234 operational sites which are managed by the Traffic Data Collection Branch. This number fluctuates due to road construction and equipment failures. For example, between February 2012 and April 2012, the number of operational ATR sites decreased from 240 to 234. Three of the sites had equipment failures with the piezoelectric loops in the pavement that are scheduled for repair. The other three sites are not operational, because there has been road construction in the area which has damaged the sites. Permanent sites are polled on a daily basis by the TPAS software. Incoming data (vehicle classification, volume, and speed) is processed through quality control checks and reviewed by office personnel. Refer to Appendix A: 13-Bin FHWA Vehicle Classification Scheme for detailed illustration on vehicle classification.
Atlanta ATR Site Locations
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Selection Criteria for Installation of a New ATR Site
When funding allows for a new ATR site to be installed, a potential new ATR site is chosen based upon defined selection criteria. Then, the Traffic Data Collection Branch makes a field inspection of any recommended new ATR site to ensure site feasibility and optimal placement for the physical installation of the ATR equipment within the traffic count segment. The Data Reporting and Quality Control Branch will review the results of the field inspection and approve the installation. The TMG states, "...that the development of seasonal factors to expand short-term counts to annual average daily traffic (AADT) is the primary objective of the continuous ATR program, and this is the objective that should carry the most weight in establishing the number and location of ATR sites operated by the state highway agency." All other considerations are secondary.

Selection Criteria

Field Evaluation

Installation of a New ATR Site

The following is a list of the selection criteria that must be considered:
1. Primary Selection Criteria a. Minimum of five to eight ATR sites per Traffic Factor Group depending upon the traffic patterns and precision desired
2. Secondary Selection Criteria a. Critical nodes on high volume roads that are used in the Step Down Method b. Replacement of ATR sites that were eliminated due to construction c. Adequate coverage in each of the seven GDOT Districts to ensure geographic differences in travel trends are captured d. Minimum of one operational ATR site per Interstate route e. Minimum of one operational ATR site on other major arterials (e.g., SR-400 and SR-316) f. Area of particular interest to GDOT management for planning purposes or to meet specific Federal requirements (e.g., Mechanistic-Empirical Design Pavement Guide of New and Rehabilitated Pavement Structures)
In the last two years due to budget constraints, OTD has only installed one new ATR site located on I-85 in Gwinnett County near Jimmy Carter Boulevard. Recently, two ATR sites on the north side of I-285 were eliminated due to construction. OTD may have to decide which of the two sites are re-installed due to funding constraints. The above selection criteria will be used in this decision.

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VI. SHORT-TERM MONITORING PROGRAM
The short-term program collects roadway segment-specific traffic count information on a scheduled cycle, collected at each segment for a 48-hour period. The short-term program can also be called the portable collection or the coverage program. The portable collection devices can be configured to collect vehicle classification counts as well as volume counts. Currently, OTD collects short-term volume counts at approximately 8,000 locations annually that are distributed statewide and include approximately 1,500 locations near bridges.
Portable collection devices are pneumatic tube(s) that are stretched across a road and secured on both sides by a field technician. They are connected to a counter on one side of the road where the data is stored. When a vehicle's axle crosses the road tube, the pulse of air that is created is recorded and processed by the traffic counter. Depending upon the type of count needed, one of several different road tube configurations may be set-up in the roadway.
There are two different types of portable collection devices used by OTD. In-house staff collects traffic data using the PEEK ADR1000 Portable Traffic Counter/Classifier. The majority of the portable traffic count collection is performed by a contractor that uses the MetroCount 5600 Series Roadside Unit. More information on the two systems can be found at the following websites:
http://www.peektraffic.com/products_data.php
http://www.metrocount.com/products/mc5600/
Number of Counts, Period of Monitoring, and the Cycle of Monitoring The Federated Road Enhanced Database (FRED) database houses the Road Characteristics (RC) file, AADT and is used in the development of HPMS. Each road system is defined by a beginning and ending mile point in FRED. The road systems are divided into smaller sections designated with Traffic Count (TC) numbers that have similar traffic volumes. Each TC number has an AADT volume.
Georgia has approximately 22,000 TC numbers or segments. It is not possible to collect traffic counts on every road segment in Georgia every year due to practical limitations. Therefore, portable traffic is collected on each road segment on an annual or cyclical basis which varies with collection intervals ranging from two to four or six years. Traffic counts that are collected on a cyclical basis are adjusted with growth factors in years when they are not counted and marked as Estimated. AADT data is marked as either Estimated or Actual for each collection year for each TC number.
Federal Regulations 23 CFR 500.204 states, "Documentation of field operations shall include the number of counts, the period of monitoring, the cycle of monitoring, and the spatial and temporal distribution of count sites." The plan for the portable traffic collection program, including the number of counts and the cycle of monitoring, is re-evaluated each year. The period of monitoring is a 48-hour interval with data recorded for every hour of each day; a typical collection time for many state Department of

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Transportations. The 48-hour data from the portable traffic sites is usually collected Tuesday through Thursday. Refer to Appendix B: 2011 and 2012 Portable Traffic Collections for further details on the number of counts and cycle of monitoring.
OTD is striving to meet the demands of internal GDOT customers by increasing traffic collection near bridges and, in the future, near railroads. In the fall of 2011, the plan was adjusted and approximately 1,500 traffic counts specifically placed near bridges were added to the 2011 program for OTD staff to collect. It should be noted that the portable collection equipment cannot be set-up directly on a bridge structure.
Collecting traffic counts near bridge and railroads will provide valuable information to our internal customers and improves their ability to make informed decisions related to their respective responsibilities. The collected data on these facilities (railroads and bridges) also improves the reliability and timeliness of other federally required reports such as Pontis and the Federal Railroad Administration reports. For reference, Pontis is a software application developed to assist in managing highway bridges and other structures.
Spatial and Temporal Distribution of Traffic Counts Trimble Recon Global Positioning System (GPS) units are used by in-house staff to record details about traffic counts (referred to as Field Notes), such as time, date, basic road characteristics, and physical location of the collected traffic count. The GIS Branch uses the GPS data to create digital maps of the actual collected traffic count sites which are reviewed for quality control. The Field Notes assist the Data Reporting and Quality Control Branch in determining the validity of a collected portable traffic count. The Field Notes are loaded into the Traffic Polling and Analysis System in conjunction with the portable traffic count files. The Field Notes also serve as notification to the Road Data Collection Branch of physical road changes.

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VII. WEIGH-IN-MOTION PROGRAM
There are 90 non-permanent sites located throughout Georgia at which portable Weigh-in Motion (WIM) data is collected. Time stamped per vehicle record traffic data is collected at 30 of these sites each year on a three year rotating cycle. According to the FHWA guidelines, 10 of these sites should be on Interstate highways. Beyond the 90 sites described above, OTD also has two permanent WIM sites installed on the Interstate Highway System. One site is located on I-75 north of Macon and the other site is located on I-285 near Orchard Road. These sites are not polled; data is retrieved at the physical location of the site on a regular basis (approximately once per month).
The permanent WIM sites collect vehicle weight, as well as vehicle classification, speed, and volume using a piezo-loop-piezo sensor configuration. The piezo-sensor utilized is a Kistler quartz piezoelectric sensor which provides 95% accuracy when collecting vehicle weight data. Temperature fluctuations do not affect the accuracy of this sensor.
Weigh-in Motion technology is used to measure vehicle counts, axle and gross weight, vehicle classification, and speed data. WIM data is used for pavement and capacity studies, enforcement and inspection purposes, and for analysis of truck transport practices. The data from these sites are provided to FHWA each year. FHWA runs the data through their software and produces summary Wtable reports, which can be viewed at the following website:
https://fhwaapps.fhwa.dot.gov/vtris-wp/
GDOT has contracted with a consultant to study how to implement the latest Mechanistic-Empirical Pavement Design Guide of New and Rehabilitated Pavement Structures recommendations. The recommendations from this study will probably call for additional permanent WIM sites; however, funding will need to be identified, because these sites are very expensive to install and maintain. OTD has provided the consultant with collected WIM data and will review the consultant's implementation recommendations when presented.

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VIII. QUALITY CONTROL AND ASSURANCE
One of the main goals of the traffic collection program is to provide an accurate portrayal of statewide traffic data and trends. With very few exceptions, OTD's collection program covers the complete State Highway System (about 18,000 miles). Every effort is made to collect the portable traffic data during typical travel conditions (excluding holidays or weekends). A one-time event, such as a county fair, is not an accurate representation of an "average day" and is not a long-term traffic trend. On the other hand, there are conditions which do influence long-term changes in traffic characteristics. The following is a list of some of these conditions: addition of lanes, new intersections/interchanges, new roads, new business or residential developments, changes in the economy, changes in land use, etc.
Quality assurance refers to efforts made throughout the traffic collection cycle to ensure a high standard of data output. For example, OTD has documented procedures and staff training for the installation and calibration for all types of equipment. Additionally, all equipment installed by a contractor is closely reviewed by the Traffic Data Collection Branch for adherence to guidelines. OTD employs the following approaches for data quality assurance:

Staff training and use of guidelines Data processing rules and checklists Proven software and data processing methods Tight control on vendors' compliance with guidelines Quality control checks with proven algorithms Stringent adherence to calibration and set-up routines for equipment

According to the TMG, "Each highway agency should have formal rules and procedures for their quality control efforts." OTD has established quality control (QC) rules and procedures that evolve in conjunction with new technologies and software enhancements which ensure accurate statewide traffic data. There are many quality control checks preformed on the traffic data by both OTD and the FHWA. For example, each month OTD submits ATR data to the FHWA online through the Travel Monitoring Analysis System (TMAS) which has built-in quality control checks. The Data Reporting and Quality Control Branch preforms quality control reviews on a daily or weekly basis and also conducts a comprehensive review as part of the annual data processing.

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IX. WEEKLY DATA PROCESSING

The weekly data processing of incoming ATR data and portable collection data is managed through two different processes mainly within one system (TPAS) which allows office personnel to quickly view the status of incoming data. Any data that does not meet standards of the established quality control rules is either rejected immediately or considered flagged data. The flagged data can be subjected to further review, as deemed necessary. Proven software and data processing methods enable OTD to efficiently process all data with a high level of quality.
Weekly Data Processing for Continuous Monitoring Sites

OTD can immediately identify the current status of every ATR site at a glance, such as: not polling, transfer errors, conversion errors, database errors, broken hardware, successful poll, multi-unit wait, unknown, atypical, and passed or failed QC rules. OTD can re-poll a particular site and also manually upload a data file to the system. Office personnel can view all details pertaining to a site regarding any issue with polling or quality control. A High Level Overview of the ATR QC Process is shown below in Figure 1:

START
If Yes Then, Poll Again
Initiate Polling (Autopoll, Manual Poll)

1st Fail to Connect

ATR
No
Maintenance

Failed Queue
No
Polling Successful

All Detail Goes to Log

All Detail Goes to Log
Review

Detailed Log
All Detail Goes to Log

Rules Thresholds Site Details
Schedule Lane Relationship Special Event/ Holiday
Results Log Status of Site Analysis View
Lane Data Classification Data

Override
Fail

If No, Day Stored
as Fail
Yes

Pass/Fail QC

TPAS Production
Server

Day Stored as Pass

Figure 1: High Level Overview of ATR QC Process

If Yes, Bin File Downloaded

The standard practice is to poll the data from ATR sites each night at 1:00 a.m. However, in inclement weather, OTD can configure the ATR sites to enable Real Time Polling in Emergency Mode which polls data from the ATR sites identified on hurricane evacuation routes every 15 minutes and has priority over the auto-poll. The data is stored in a directory on the TPAS server and is retrieved by the Emergency Operations Center (EOC) for critical planning and use.

ATRs are categorized into groups, such as Interstates or low volume, which apply specific quality control rules. The system also has adjustable thresholds for quality control rules, when applicable. The QC rules check for various issues, such as incoming data format, volume minimums/maximums, vehicle classification comparisons, atypical days (holidays or special events), etc. Also, double-sided ATR stations are checked to ensure that both sides of the roadway are operational. A complete list of the Quality Control Rules for ATR Data Collection can be viewed in Table 1 on the following page:

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Table 1: Quality Control Rules for Continuous Monitoring Sites

Quality Control Rule

Description

All Counts/ One Bin

The system will reject the data if all the traffic for one vehicle class bin is in one lane for the day.

Maximum Threshold

Atypical Day or Holiday
Class 1 Greater than Class 2

The system will accept data that would have been marked as flagged based upon a predetermined list of atypical days or holidays. It will not accept incomplete data. The system will flag any day(s) where the volume in vehicle class 1 exceeds the volume in vehicle class 2.

Class 14 Exceeds X

The system will flag the day(s) that have vehicles in class 14 greater than X percent of the total volume.

0.7%

Class 15 Exceeds X

The system will reject the day(s) that have vehicles in class 15 greater than X percent of the total volume.

0.7%

Class 3 Greater than Class 2

The system will flag any day(s) where the volume in vehicle class 3 exceeds the volume in vehicle class 2.

Class 8 Greater than Class 9

The system will flag any day(s) where the volume in vehicle class 8 exceeds the volume in vehicle class 9.

Daily Directional Volume The system will flag the entire set of counts if volume in one

70%

Check

direction is over X percent of the total volume. This check is

not applied to non- directional data.

Daily Ratio of Class 2 to The system will flag any day(s) where the daily total of vehicle

56%

Daily Total

class 2 data is greater than X percent of the total volume.

Less than 24 Hours of Data

The system will reject any blank volume in one direction.

Max Zeros

The system will reject the data if there are more than X

7

consecutive hours of zeros.

Missing Lane Data

The system will reject the data if there are no vehicle counts

during the day for a lane or not enough data records have

been provided. There should be one data record for each hour

for each lane defined in the incoming data.

Multi-Unit Wait

The system will assign the ATR unit that has data (double-side

sites only) with the temporary status of MULTI_UNIT_WAIT until data for the 2nd side is received.

Sum of Combination

The system will flag any day(s), where the total of the volumes

Vehicles Exceeds Class 9 in vehicle classes, 11, 12, and 13 exceeds the volume in vehicle

class 9.

Zero Bound

The system will reject any day that has an hour with zero

50

vehicles that has the immediate hour before and after the zero

with a volume over X vehicles.

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Weekly Data Processing for Short-Term Monitoring Sites

Portable traffic data collected by field technicians is processed on a daily or weekly basis by office personnel. Counties are closed out as the portable data collection is completed. Refer to Appendix C: Georgia Counties and Federal Information Processing Standards (FIPS) Identification Numbers for a list of counties. In Figure 2: Status of 2012 Portable Traffic Collection as of 5/30/2012, 54% of the portable traffic collected has passed quality control (indicated in green); 2% has failed, has been marked uncountable or is parked (indicated in yellow); and 44% not been completed, yet (indicated in red). The collection status is typical for this time of year.

As discussed in section V. Short-Term Monitoring Program, GPS data and Field Notes collected at every portable data collection site assist with the quality control of the traffic count. Regarding

Figure 2: Status of 2012 Portable Traffic Collection as of 5/30/2012

GPS, office personnel compare the offset measured in meters between the current year and the last

year of data collection. Recorded GPS data coordinates need to be within the assigned TC segment.

If incoming traffic data is flagged, office personnel perform further analysis, such as: evaluate GPS data coordinates, review the QC rule that the count has failed, view historical comparison for site, study trend analysis graphs, and compare traffic count data from adjacent sites. A complete list of the Quality Control Rules for Portable Data Collection can be viewed in Table 5.

Portable counts can be assigned into different categories: passed, failed, uncountable, reviewed, assigned, QC/load error, parked, or not reviewed. If a count has failed, the office personnel can assign it to a parked category where it will wait until the 2nd count data comes in for comparison. One, none or both counts can be accepted at that time. There is a comment box where reasons for the decision can be noted. A High Level Overview of the Portable QC Process is shown below in Figure 2:

Determine the Traffic Collection
Plan

No, delete and reload

Create Maps, Assign Traffic Count Sites, and Program GPS
Units

Collect Portable Traffic, GPS, Field Notes

Data uploaded to Application

Successful upload
Yes

QC Review of Failed Count
QC Rules GPS/ Field Notes Special Event/
Holiday Historical Data Trend Analysis

Fail, but reset is ordered
Figure 3: High Level Overview of the Portable QC Process

Marked as `Fail' in application
No

Yes
Override
Fail

Marked as `Pass' in application

Pass/Fail QC

Pass

and Reset??

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Table 2: Quality Control Rules for Short-Term Monitoring Sites
Quality Control Description Rule Blank (No Data) The system will reject any blank volume in one direction. Check

Minimum Maximum

Threshold Threshold

--

--

Class 14

The system will flag the day(s) that have vehicles in vehicle

--

5%

class bin 14 greater than X percent of the total daily

volume.

Class 15

The system will flag the day(s) that have vehicles in vehicle

--

1%

class bin 15 greater than X percent of the total daily

volume.

Class 3 greater The system will flag any day where the volume in vehicle

--

--

than Class 2

class bin 3 exceeds the volume in vehicle class bin 2.

Daily Directional The system will calculate the directional distribution (D Volume Check Factor) of the traffic. If the D Factor is greater than X
percent, the counts are flagged.

--

70%

Daily Ratio of The system will compare the ratio of vehicle class 1 bin

--

--

Class 1 to 2

data to vehicle class 2 bin data. If class 1 is higher, the

data for the day will be flagged.

Direction Check
Factor AADT Outside Range

The system will check that the direction for the site is correct. The system should PASS a 0 (non-directional) OR a pair (1:3 OR 2:4) at every TC Number. It would NOT accept a lone direction or an incorrectly matched directional pair (example: North-1 and East-2). The system calculates the AADT based on the factor groups using daily, monthly, and axle factors. Then, the system compares the computed hourly AADT to the historical AADT and will flag sites that are outside the established volume group tolerances limits.

--
Variable

--
Variable

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Quality Control Rule Historical Volume Check for Portable
Hourly Zero Volume Check

Description
The system averages the last 3 years of the AADT history. If 3 years of data is not available, the system will average the last 2 years of the AADT history. If 2 years is not available, the system will use one year of AADT history. The data is flagged, if it is outside the volume group tolerance limits. The system will reject any hour with zero volume in one direction when the current AADT for the site is greater than 10,000.

Minimum Maximum Threshold Threshold Variable Variable

--

10,000

Less Than 48 The system should reject the entire set of counts if there

--

Hours of Data are not at least 48 hours of data. This means one or more

row(s) in a PRN file is missing. If a row has a blank PRN

file, the system still counts the row.

Max Hourly

The system will reject the entire set of counts with an

--

Volume

hourly volume count of greater than X

--
5,000

Midnight/ Noon The system will reject the entire set of counts, if the

Check

midnight count is higher than the noon count.

--

--

Peak Hours (6-9 The system will reject the entire set of counts with an

--

a.m.) (3-6p.m.) hourly volume count of zero between the hours of 6 a.m.

9 a.m. and 3 p.m. 6 p.m. when the functional class is not

equal to 9 or 19.

Portable Truck The system will calculate the truck percent by adding

--

Percent

vehicle class bins 4 - 14 for the day and dividing by the

total daily traffic count. Incoming data will be flagged, if

the truck traffic is greater than X percent.

Sum of

The system will flag any day, where the total of the

--

Combination volumes in vehicle class bins 11, 12 and 13 exceeds the

Vehicles

volume in vehicle class bin 9.

Exceeds Class 9

Volume Check The system will flag any incoming data if there is an hourly

0

volume count of greater than 9999. Allowable volumes

are from 0 to 9999.

--
40%
-9,999

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Georgia DOT

Office of Transportation Data

X. ANNUAL DATA PROCESSING

Annual data processing is a cycle that involves planning, traffic data collection, quality control, traffic calculations, reporting and publishing. Planning begins in November. Portable traffic collection begins in mid-January and ends around the beginning of November. The comprehensive review of the annual traffic begins in January. Refer to Appendix D: Traffic Calculations for further detail on traffic calculations. Reporting and publishing is usually in February or March. The following is a list of tasks that are performed during Annual Data Processing:
1. Establish the Plan a. Review TC segmentation b. Review collection cycle for portable data c. Compare TPAS site information and planned collection (Coverage List)

Update Systems and Report Traffic
Calculate Estimates/
Factors

Establish the Plan
Review Annual Traffic

Implement the Plan
Collect Traffic

2. Implement the Plan a. Synchronize the Coverage List and TPAS b. Create maps and lists of portable traffic count locations for field technicians c. Program GPS Trimble Units

Figure 4: High Level Overview of Annual Data Processing

3. Collect Traffic a. Collect and review (QC) portable data, including Field Notes, GPS Data and Traffic Data Files b. Poll and review(QC) ATR data

4. Review Annual Traffic a. Ensure all portable and continuous traffic has been collected and has passed quality control standards

5. Calculate Estimates/ Factors a. Estimate AADTs at uncounted TC sites based upon historical data and current year ATR data b. Calculate traffic on high volume roads (Step Down Method) c. Estimate traffic on local roads d. Calculate traffic adjustment factors e. Calculate peak hour traffic data and K-factors

6. Update Systems and Report Traffic a. Populate the Federal Reporting Enhanced Database with traffic data b. Provide traffic data for external public viewing (GA STARS and ATR Reports) c. Report traffic data to the FHWA in the HPMS submittal

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Georgia DOT

Office of Transportation Data

Management of Traffic Count Segments
According to the HPMS Field Manual, "Selection of count station locations should be based on previous count experience, recent land developments, and the existence of uncounted sections along the routes." Although TC segments were initially created to be homogenous (i.e., similar traffic for the entire segment); traffic has a fluid dynamic and, as such, updates must be made annually in order to maintain the integrity of the segments. Break points are added, deleted, or moved to reflect changes reported in the road inventory and actual field conditions.
OTD evaluation criteria for adding and spacing TC segments are as follows:
TC segments must meet Federal-aid eligibility requirements. Federal-aid roadways are any public road with a functional classification higher than 8, 9, or 19 (considered local roads). Local roads are randomly sampled for traffic data reporting; meaning only select locations on local roads have TC numbers.
Typically, and wherever possible, segments should span from major intersection to a major intersection or a major traffic generator. A major intersection is defined as an arterial roadway. An example of a major traffic generator is an entrance/exit to a major retail store, such as a Super Wal-Mart.
The Data Reporting and Quality Control Branch office personnel evaluate a road's segmentation if adjacent AADT volumes are varying by 20% or more. In connection with this effort, the last three or more years of traffic history is considered during the analysis.
New business requirements may require additional TC segments. For example, OTD added traffic count segments containing bridges to the coverage program in 2009.
OTD evaluation criteria for retiring a TC segment are as follows:
If there is a re-classification in functional classification which makes the road a local road (FC 8, 9 or 19) without the presence of a bridge or railroad, the TC number would be retired.
Also, OTD reviews and evaluate sample sites if adjacent segments have less than 5% difference in the AADT volumes. If the evaluation process supports a modification, OTD will delete a sample and expand the terminus of the adjacent TC segment.
Additionally, there could be a change in Federal requirements or funding levels.
There may also be cases where it is not safe or feasible for a field technician to collect the data.

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Calculation of Traffic on High Volume Roads (Step Down Method)

GDOT uses the ramp counting procedure described in FHWA's TMG to estimate AADT volumes for Interstates and freeways. It is referred to as the Step Down Method, which is also known to some states as Ramp Balancing. The high volumes on these roads make them impossible to collect with a portable collection device due to the safety of the field crew. For example, the main Interstate through Atlanta, I-75, has an AADT (2011) of 313,380, and ramps at the I-285 and I-85 interchange in Gwinnett (also known as Spaghetti Junction) have AADTs (2011) around 40,000.
The Step Down Method involves counting all entrance and exit ramps between two established mainline anchor points (or nodes) and then reconciling the count data to calculate the mainline AADT. As shown in Figure 5: Example of Step Down Method, the calculated AADTs reduce in volume or `step down' from TC0927 to TC0446. The ramps are counted using either portable collection devices or, in a few locations, PTMS sites. OTD makes every effort to use ATR sites as nodes.
An AADT for each uncounted mainline link is calculated by addition or subtraction of ramp AADT (multiplied by an adjustment factor) to or from mainline AADT, starting from one anchor point/node. The adjustment factor is in accordance with the TMG which states, "The allocation of the volume difference to the ramps (and subsequently to the mainline volume estimates) is carried out by proportionally distributing the volume difference remaining at the ending control point to each of the ramps. The adjustment to each ramp is computed as the ratio of the difference in volume (remaining at the end of the reconcilement) to the sum of the ramp volumes."

Figure 5: Example of Step Down Method

8,179 4,604

7,915 5,842

7,268 5,012

8,153 4,922

8,256 3,295
8,373 2,416

9,502 3,163 8,747 2,267

In the past, the process was time-consuming and labor intensive, because it was performed manually. Currently, the processing for the Step Down Method is calculated using a computer program after the AADTs have been calculated for the ATR sites. OTD currently does not calculate the AADT volumes derived by the Step Down Method by direction of travel.

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Georgia DOT

Office of Transportation Data

Traffic Count Collection and Estimation on Local Roads
According to the FHWA, "States are required to report annually to the Federal Highway Administration (FHWA) aggregate estimates of VMT on the rural minor collector and local functional systems in rural, small urban and urbanized areas." Collectively, these are referred to as local roads which are defined as roads with a functional classification of 8, 9 or 19. Examples of local roads are a subdivision road or an unpaved country road. Generally, except for the local roads, OTD collects traffic data on all types of roads in Georgia.
On local roads, OTD collect a small number of samples to derive and compute VMT statistics for Federal reporting purposes. The total local road mileage is approximately 89,687 miles, as of the original draft date of this document (April 2012). OTD has exceeded the HPMS sampling requirements with the total number of collected local traffic counts ranging from 800-1600 for the past several years.
According to the HPMS Field Manual, "Statistically speaking, a universe is a population from which a sample is taken. A population can be any set of sampling units, such as objects that can be observed or people who can be surveyed. A sampling frame is a list of all the sampling units in a universe." In our case, the universe for local roads is the total local road mileage. The sampling unit is a randomly selected local road segment stratified by six local road types: Urban Local Not Atlanta, Urban Local Atlanta, Small Urban Local, Rural Paved, Rural Unpaved, and Dead-end/ Cul-de-sac.

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Office of Transportation Data

Traffic Adjustment Factors

Federal Regulations 23 CFR 500.204 states, "The procedures used by a state to edit and adjust highway traffic data collected from short-term counts at field locations to estimates of average traffic volume shall be documented." The raw hourly counts from portable traffic collection devices for a 48-hour period are adjusted by monthly, daily and axle factors to determine the AADT. Factors are used to estimate "average" conditions and to account for variability in the traffic stream. They are based on data provided by the ATRs and are currently calculated annually in TPAS.

Monthly factors are calculated by dividing the AADT by the monthly average daily traffic (MADT) for each location. In Georgia, January is usually the month with the lowest traffic volumes. Therefore, portable traffic collected in January would have the highest monthly factors. Daily or day-of-the-week factors are calculated by dividing the AADT by the average daily traffic (ADT). Typically, the day of the week with the lowest traffic volumes is Sunday which consequently has the highest daily factors. Axle correction factors are developed based on data that represents all seasons of the year. The axle correction factors are applied to raw counts taken with portable traffic counters which register two axle impacts as one vehicle. It is used to account for vehicles with more than two axles, typically trucks with three or more axles, in the traffic stream on a particular type of road. They should be applied to all counts that are based on axle sensors. Rural Interstates have the lowest axle factors, because they have the highest percentage of truck traffic in Georgia.

OTD plans to review our factoring approach every year based upon a variety of factors: additional ATR sites that are installed, traffic trends/patterns, high growth areas, truck traffic patterns, etc. The ATRs are currently grouped into 16 traffic factor groups (refer to Table 6: Factor Groups). As expected, Atlanta has significantly different traffic patterns compared to the rural areas of the state. The 2011 factors are shown in the following tables:

Table 3: 2011 Axle Factors

Factor Group* Axle Factors

1

0.97

2

0.94

3

0.91

4

0.78

5

0.78

6

0.78

7

1.00

8

0.95

9

0.89

10

0.99

11

0.98

12

0.97

13

0.99

14

0.99

15

0.95

16

0.87

*Factor Groups are described in Table 6: Factor Groups.

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Table 4: 2011 Daily Factors

Factor Group* Sun

1

0.99

2

0.99

3

1.02

4

1.07

5

1.07

6

1.06

7

0.97

8

0.99

9

1.00

10

0.95

11

0.96

12

0.97

13

0.96

14

1.00

15

0.99

16

0.97

Mon Tues Wed Thu Fri Sat 0.98 0.98 0.95 0.89 1.04 1.26 0.97 0.97 0.93 0.87 1.07 1.29 1.01 1.00 0.95 0.85 1.03 1.20 1.10 1.07 0.97 0.86 0.97 0.99 1.09 1.07 0.98 0.84 1.01 1.00 1.10 1.08 0.98 0.83 1.02 0.98 0.97 0.95 0.94 0.90 1.13 1.26 0.97 0.97 0.93 0.86 1.06 1.37 0.99 0.98 0.93 0.86 1.08 1.25 0.93 0.92 0.92 0.90 1.18 1.38 0.94 0.94 0.92 0.86 1.11 1.47 0.95 0.94 0.92 0.87 1.10 1.45 0.94 0.93 0.92 0.89 1.11 1.45 0.97 0.95 0.94 0.90 1.04 1.34 0.97 0.96 0.93 0.90 1.08 1.25 0.95 0.94 0.92 0.89 1.11 1.34

Table 5: 2011 Monthly Factors

Factor Group* Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

1

1.07 1.00 0.98 0.96 0.97 1.02 1.04 1.00 0.98 0.98 1.02 1.02

2

1.06 0.99 0.98 0.97 0.98 1.01 1.04 1.00 0.99 0.99 1.00 1.01

3

1.10 1.02 1.00 0.98 0.99 0.98 0.97 1.01 1.00 0.95 1.00 1.02

4

1.11 1.05 0.95 0.97 1.00 0.93 0.91 1.02 1.05 1.00 1.02 1.06

5

1.14 1.08 1.03 0.97 0.98 0.94 0.89 0.98 1.01 1.01 1.02 1.04

6

1.16 1.08 0.99 0.94 0.98 0.91 0.87 1.01 1.04 1.01 1.04 1.07

7

1.07 1.03 1.00 0.99 0.99 0.99 1.04 0.97 1.00 1.00 1.00 0.96

8

1.06 0.99 0.98 0.98 1.00 1.00 1.01 1.00 1.00 1.01 1.00 0.98

9

1.07 1.00 0.95 0.97 1.00 0.97 0.99 1.01 1.02 1.01 1.00 1.01

10

1.05 0.98 0.96 0.97 0.98 1.02 1.07 0.99 0.98 1.01 1.00 1.01

11

1.03 0.94 0.95 0.96 1.00 1.03 1.06 1.00 1.00 1.02 1.01 1.01

12

1.05 0.98 0.97 0.97 0.99 1.00 1.03 1.00 1.00 1.02 1.00 1.00

13

1.07 1.00 0.97 0.98 0.99 1.00 1.02 0.97 0.98 1.01 1.01 1.01

14

1.06 1.00 0.98 0.99 0.99 1.00 1.03 0.98 0.99 1.01 1.00 0.98

15

1.07 1.02 0.99 0.98 0.99 0.98 0.98 0.99 1.00 1.00 1.01 1.01

16

1.09 1.00 0.97 0.97 0.99 0.97 0.99 0.99 1.00 1.03 1.02 1.01

*Factor Groups are described in Table 7: Factor Groups.

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Table 6: Factor Groups
No. Factor Group

1

Rural - Local Collectors

2

Rural - Minor Arterial

3

Rural - Major Arterial

4

Rural - I-75

Description
Local roads or collectors in a rural area which provide low levels of travel mobility (e.g., a subdivision road or intracounty travel corridor) Routes which provide service to corridors with trip lengths and travel densities greater than that of collectors or local roads (e.g., Appling County SR-15) Routes which have a trip length and travel density indicative of substantial state wide travel (e.g., Bartow County SR-20)
I-75 Outside of an Urban Area

5

Rural - I-85

I-85 Outside of an Urban Area

6

Rural - Interstates

Interstates that are accessed only using ramps and are outside of an Urban Area (e.g., I-16 in Bryan County)

7

Small Urban - Local Collector Local roads or collectors in a small urban area which provide

low levels of travel mobility (e.g., a subdivision road or intra-

county travel corridor)

8

Small Urban - Arterial

Routes of moderate to high lengths and travel that are

within a small urban area (e.g., Bulloch County SR-67

Bypass)

9

Small Urban/Urban - Freeways Freeways, Expressways and Interstates which are restricted

Interstate (Not Atlanta)

access roadways and not in Atlanta (e.g., I-95)

10 Urban - Local Collector

Local roads or collectors in an urban area which provide low

levels of travel mobility (e.g., a subdivision road or intra-

county travel corridor)

11 Urban - Minor Arterial

Routes that serve the major centers of activity with the

(Not Atlanta)

highest traffic volumes and the longest trip lengths not in

Atlanta (e.g., Catoosa SR-146)

12 Urban - Major Arterial

Routes that serve the major centers of activity with the

(Not Atlanta)

highest traffic volumes and the longest trip lengths not in

Atlanta (e.g., Catoosa SR-146)

13 Urban - Minor Arterial (Atlanta) Routes which provide trips of moderate length linking

principal arterials in Atlanta (e.g., Fulton County SR-3)

14 Urban - Major Arterial (Atlanta) Routes that serve the major centers of activity with the

highest traffic volumes and the longest trip lengths in

Atlanta (e.g., Cobb County SR-5)

15 Urban - Freeways Interstate

Freeways, Expressways and Interstates which are restricted

(Atlanta)

access roadways and are in Atlanta (e.g., I-75, I-85, SR-400,

I-985)

16 Urban - I-285 (Atlanta)

I-285 Loop

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Georgia DOT XI. OTHER CONSIDERATIONS

Office of Transportation Data

A complete analysis of any program identifies and considers all relevant issues and challenges. The main program management challenge is balancing costs, resources, and statistical data needs. In a world not constrained by funding or other resources, every TC segment on every road would have actual traffic data count available every year. Perhaps, in a small geographical area with a large budget this is an actual possibility. However, as is the case with most state Department of Transportations, budget constraints must be continually balanced with resources (time and available staff) and the needs (quantity and quality of traffic counts collected). It is the classic paradox of project management.

Costs Resources

Needs

Despite budget constraints, the demand for traffic data in all formats has not been reduced. For example, the most recent HPMS reassessment is requiring additional traffic data to be collected on ramps. Special requests for traffic counts are also a competing factor with the portable traffic count program. Often, these traffic counts revolve around a special event and are not valid for use in an AADT calculation. As previously mentioned, OTD has also added traffic counts specifically located near bridges to meet internal data needs.

Other challenges include relational database struggles, software integration, staffing issues, and making traffic data accessible to the public in an easy-to-use interface. Most of the traffic data customers want an easy-to-use, simple interface that provides traffic counts. Other customers want all types of traffic data in detail as soon as it is available to them. OTD has made significant strides towards making data more accessible to the public and is continually exploring how to better serve customers.

In regards to traffic data collection, safety of the traffic data collection crew is the primary concern in collecting data on high-volume routes. Due to equipment failures, collecting traffic data in stop-and-go traffic conditions is a challenge. Increased traffic congestion increases the difficulty in obtaining reliable vehicle classification counts. Construction and incidents also impact traffic data collection activities. Data processing, and quality control and assurance are challenges especially for high traffic-volume routes. Atlanta, in particular, as a metropolitan area with approximately five million people has significant traffic congestion, construction, and traffic incidents.

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REFERENCES
American Association of State Highway and Transportation Officials (AASHTO), United States. (2009). AASHTO Guidelines for Traffic Data Programs.
Federal Regulations, Title 23: Highways, Part 500-Management and Monitoring Systems, Subpart BTraffic Monitoring Systems, 500.201-204. Retrieved April 10, 2012 from http://ecfr.gpoaccess.gov/cgi/t/text/textidx?c=ecfr&rgn=div5&view=text&node=23:1.0.1.6.14&idno=23
Georgia Department of Transportation, Office of Transportation Data. (June 2008). Traffic Data Collection Guide.
National Cooperative Highway Research Program, Transportation Research Board, National Research Council. (2008). Mechanistic-Empirical Pavement Design Guide of New and Rehabilitated Pavement Structures. Retrieved April 30, 2012, from http://onlinepubs.trb.org/onlinepubs/archive/mepdg/home.htm
Randall, James L. (February 1, 2012). Texas Department of Transportation, Traffic Recorder Instruction Manual. Retrieved April 30, 2012 from http://onlinemanuals.txdot.gov/txdotmanuals/tri/images/FHWA_Classification_Chart_FINAL.png
U.S. Department of Transportation, Federal Highway Administration, Office of Highway Policy Information. (March 2012). Highway Performance Monitoring System Field Manual.
U.S. Department of Transportation, Federal Highway Administration, Office of Highway Policy Information. (Last Update: April 4, 2011). Traffic Monitoring Guide. Retrieved May 1, 2012 from http://www.fhwa.dot.gov/ohim/tmguide/index.htm

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Office of Transportation Data

Appendix A: FHWA 13-Bin Vehicle Classification Scheme

Source: Texas Department of Transportation's illustration of the FHWA 13-Bin Vehicle Classification Scheme

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Office of Transportation Data

Appendix B: 2011 and 2012 Portable Traffic Collections

Table B-1: 2011 Portable Traffic Collections (Planned)

Road System

Cycle

Volume Only Traffic Counts

State Routes
Off-System Federal -
Aid
Non Federal-Aid Locals2 Critical Ramps3 Major Ramps4 Other Ramps5

2 Year 4 Year
6 Year
Annual 2 Year 4 Year

2,100 1,700
1,300
615 350 250

Classification Traffic Counts
1,989 2981
200
---Total

PTMS Counts
11 2
35

Total Traffic Counts 4,100 2,000
1,500
650 350 250 8,850

Table B-2: 2012 Portable Traffic Collections (Planned)

Road System

Cycle

Volume Only Traffic Counts

State Routes
Off-System Federal-
Aid
Non Federal-Aid Locals2 Critical Ramps3 Major Ramps4 Other Ramps5

2 Year 4 Year
6 Year
Annual 2 Year 4 Year

2,367 1,623
1,034
615 350 244

Classification Traffic Counts
1,629 3711
359
--6

PTMS Counts
11 2
--
35 --Total

Total Traffic Counts 4,007 1,996
1,393
650 350 250 8,646

Footnotes:
1. The Off-System Federal-aid vehicle classification counts are on offsystem HPMS sample locations and National Highway System (NHS) Intermodal facilities.
2. Non Federal-aid local counts include bridges and railroads. 3. The ramp program will be divided into its own program based on priority to step-down, urban areas, and HPMS needs.
Critical ramp interchanges are defined as the following: a. Interstate-to-Interstate b. Interstate-to-Freeway c. Strategic Atlanta Exits/Interchanges (High Volume Corridors): I-285, Inside Perimeter, I-85 in Gwinnett, I-75 in Cobb,
and GA-400 in Fulton 4. Major ramp interchanges are defined as the following:
a. Other Atlanta Urbanized Area Boundary Interchanges b. I-95, I-516, I-520 Locations (Not Already in Critical Ramp Category) c. Other Step-down Interchanges 5. Other ramp interchanges are defined as the following: a. All other Step Down interchanges (rural locations) b. All other HPMS qualifying ramps not used in Step Down calculations

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Appendix C: Georgia Counties and FIPS Identification Numbers

County APPLING ATKINSON BACON BAKER BALDWIN BANKS BARROW BARTOW BEN-HILL BERRIEN BIBB BLECKLEY BRANTLEY BROOKS BRYAN BULLOCH BURKE BUTTS CALHOUN CAMDEN CANDLER1 CARROLL CATOOSA CHARLTON CHATHAM CHATTAHOOCHEE CHATTOOGA CHEROKEE CLARKE CLAY CLAYTON CLINCH COBB COFFEE COLQUITT COLUMBIA COOK COWETA CRAWFORD CRISP

Code 001 003 005 007 009 011 013 015 017 019 021 023 025 027 029 031 033 035 037 039 043 045 047 049 051 053 055 057 059 061 063 065 067 069 071 073 075 077 079 081

County DADE DAWSON DECATUR DEKALB DODGE DOOLY DOUGHERTY DOUGLAS EARLY ECHOLS EFFINGHAM ELBERT EMANUEL EVANS FANNIN FAYETTE FLOYD FORSYTH FRANKLIN FULTON GILMER GLASCOCK GLYNN GORDON GRADY GREENE GWINNETT HABERSHAM HALL HANCOCK HARALSON HARRIS HART HEARD HENRY HOUSTON IRWIN JACKSON JASPER JEFF-DAVIS

Code 083 085 087 089 091 093 095 097 099 101 103 105 107 109 111 113 115 117 119 121 123 125 127 129 131 133 135 137 139 141 143 145 147 149 151 153 155 157 159 161

County JEFFERSON JENKINS JOHNSON JONES LAMAR LANIER LAURENS LEE LIBERTY LINCOLN LONG LOWNDES LUMPKIN MCDUFFIE MCINTOSH MACON MADISON MARION MERIWETHER MILLER MITCHELL1 MONROE MONTGOMERY MORGAN MURRAY MUSCOGEE NEWTON OCONEE OGLETHORPE PAULDING PEACH PICKENS PIERCE PIKE POLK PULASKI PUTNAM QUITMAN RABUN RANDOLPH

Code 163 165 167 169 171 173 175 177 179 181 183 185 187 189 191 193 195 197 199 201 205 207 209 211 213 215 217 219 221 223 225 227 229 231 233 235 237 239 241 243

County RICHMOND ROCKDALE SCHLEY SCREVEN SEMINOLE SPALDING STEPHENS STEWART SUMTER TALBOT TALIAFERRO TATTNALL TAYLOR TELFAIR TERRELL THOMAS TIFT TOOMBS TOWNS TREUTLEN TROUP TURNER TWIGGS UNION UPSON WALKER WALTON WARE WARREN WASHINGTON WAYNE WEBSTER WHEELER WHITE WHITFIELD WILCOX WILKES WILKINSON WORTH

Code 245 247 249 251 253 255 257 259 261 263 265 267 269 271 273 275 277 279 281 283 285 287 289 291 293 295 297 299 301 303 305 307 309 311 313 315 317 319 321

Footnote: 1. Numbers 041 and 203 have been deliberately omitted.

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Appendix D: Traffic Calculations

Description Annual Vehicle Miles Traveled (AVMT) ATR AADT

Equation* Daily Vehicle Miles Traveled * 365
Sum of Total Yearly Traffic Volume/ Total Number of Operational Days

Axle Factors

Total Vehicle Volume / (Total Axle Strikes/ 2)

D or Directional Distribution Factor Daily Factors

Predominate Direction of Peak Hour Volume/ Total Peak Hour Volume AADT/ Average Daily Traffic

Daily Vehicle Miles Traveled (DVMT or VMT) K or Design Hour Factor

Length of Roadway Segment * AADT 30th Highest Hour/ AADT

Monthly Factors

AADT/ Monthly Average Daily Traffic

Portable AADT (Classification) Portable AADT (Volume Only) Simple Sample Size Calculation

24-hour Short-Term Volume * Daily Factor * Monthly Factor
24-hour Short-Term Volume * Daily Factor * Monthly Factor * Axle Factor
n= t x p(1-p) m

Truck Percentages

Description: n = Required Sample Size t = Confidence Level at 99% (Standard Value of 2.576) p = Population m = Margin of Error at 5% (Standard Value of 0.05) (Sum of Vehicles in Classes 4-13/ Total Sum of Vehicles) * 100

Footnotes:
1. The list above is intended to be a basic list of equations. It should be noted that additional steps, such as summation or averaging, may be necessary before an equation listed above can be applied to the data.
2. Data that has not been accepted based upon the established QC rules is omitted from any calculation.

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