Tennessee Model Users Group Organizational Meeting December 2, 2004
Introduction Steve Allen Transportation Manager 2 Traffic Planning & Statistics Office Planning Division TDOT
Education Associate of Engineering: Architectural Engineering Nashville State Technical Institute Bachelor of Science: Civil Engineering Tennessee State University
Background 28 year TDOT employee Design and Surveys 11 Years 17 years in Traffic Engineering Associate Member American Society of Civil Engineers Secretary/Treasurer Institute of Transportation Engineers
Traffic Planning & Statistics Office Steve Allen, Transportation Manager 2 The objective of our office is to collect, analyze, maintain, and distribute traffic data for the roadway system
Traffic Planning & Statistics Office Traffic Planning & Surveys Section Traffic Statstics & Safety Planning Section
Traffic Planning & Statistics Office Traffic Planning & Surveys Tony Armstrong Transportation Manager 1 Traffic Planning develops and test assumptions to forecast present and future traffic on Network and Project reports Traffic Surveys collects traffic volumes, vehicle classifications, occupancy, and vehicle weights
Traffic Surveys
Tube Count There are 11,995 regular counts made with some occurring every year and others occurring on a 2 to 3 year cycle.
Ramp Count There are 886 Ramp Counts made every year
Weigh-in-Motion Count There were 140 Truck Classification counts and 22 statewide Weigh-in-Motion counts made in 2003
Turning Movement Count In 2003 there were 74 Turning Movement Counts executed. There have been 43 so far for 2004
Traffic Forecasting Forecasting future traffic in Tennessee Capacity Analysis Traffic Simulation Reviewing and approving traffic data for all users (MPO, Consultants, Counties, Cities, etc.)
Traffic Forecasting Transportation Record 1203 Traffic Volume forecasting Methods For Rural State Highways Developing future traffic estimates is not an exact science.
Traffic Forecasting Statistics Tennessee traffic monitoring consists of thirty (30) Automatic Traffic Recorders (ATR) and nearly twelvethousand(12,000) coverage count (cycle count) locations on an annual / rotating basis. Chattanooga, Memphis, Knoxville & Nashville feature eight hundred eighty six (886) additional ramp traffic counts
The Forecasting group was responsible for 378 projects in 2003
Design Hour Volume (DHV) DHV = Peak Hour traffic volume multiplied by the factor TDOT uses the Thirty (30th) highest hour. Allows for fluctuations in daily traffic count.
Example: DHV Peak hour/ Total 24 hour volume 3846 / 58816 = 6.5% 7% 7% * 1.2 = 8.4% 9% DHV TDOT uses a standard 1.2 factor for 30 th Highest Hour.
Purpose: To measure the traffic fluctuation within one hour Peak Hour Factor (PHF) PHF = HourlyVolu me Max. RateofFlow Explanations: The most complex variation in traffic occurs by hour The peak hour of traffic volume represents the most critical period for traffic operations Capacity and other traffic analysis focus on the peak hour The relationship between hourly traffic volume* and the maximum rate of flow** within the hour is defined as Peak Hour Factor (PHF) Time Period Rate of Flow - Volume (veh.) 5:01 5:15 1800 5:16 5:30 1950 5:31 5:45 2200 5:46 6:00 2050 Total 8000 PHF = 8000/{4 x 2200} = 0.91 *Traffic volume is the total number of vehicles **Rate of flow is equivalent hourly rate
Peak-Hour Factor (PHF) PHF higher for oversaturated conditions PHF lower for under saturated conditions Approximations can be used in the absence of field measurements 0.95 is a reasonable approximation for congested conditions Default Values may be used in absence of local data. 0.92 for Urban Areas 0.88 for Rural Areas Source: Highway Capacity Manual 2000
No one can perfectly forecast the future. TDOT has the tools and expertise to provide substantiated traffic volumes and forecasts
Traffic Statistics & Safety Planning Section Harold Dilmore, Transportation Manager 1 Traffic Statistics is responsible for maintenance of traffic information in the ADAM and TRIMS systems, annually produces the Tennessee City and County Traffic Maps Book, produces all traffic maps and maintains and updates ADT Book and Traffic History websites, annually produces the HPMS to the FHWA. Safety Planning maintains the state s Traffic Crash Database and prepares Crash statistics in an attempt to identify and evaluate crash sites and hazardous areas to improve overall safety of Tennessee roadways
Traffic Statistics
ADAM (Advanced traffic Data Analysis and Management)
Question: We have access to live data in ADAM and TRIMS through a VPN connection with TDOT although I need some training and/or a user's guide in order to be able to fully utilize these programs.
ADAM is best viewed at 1024 x 768 pixels. To Login: Because everyone has viewer rights, you can either enter, in small-case letters, viewer for both User Name & Password or just click on the upper right-hand X.
To see the count history: First, Click on Coverage.
Next, Click on Trend Data.
Choose the County from the drop-down list.
Choose the Station Number you want to look at. ( If there is a Y under the Out column, that means that this Station is no longer being counted. There may be a traffic history, but it is no longer an active Count Station.) To see a graph of this location, choose the Graph button in the lower right-hand corner.
The red line is a mean average of each of the years. The blue line shows the peaks / valleys of each individual year. To print, choose the Print Graph button. To analyze the yearly growth rate, choose the Trend Analysis button.
Question: What is the procedure used by ADAM to "correct" ADT counts (sometimes an "actual" count is given that is quite a bit different)? Are hourly counts going to be made available on the web? Answer: Hourly counts are available through VPN but will probably not be available on the web.
Sample print:.
The 3rd column is the Average Weekday Traffic. This is the raw (actual) count without any factors applied. The 4th column is the Average Daily Traffic. This is the traffic with the variation (monthly and day-of-week) factor applied. The 5th column is the Adjusted Average Daily traffic. This is the Average Daily Traffic with the Truck factor applied. This is the published traffic; the traffic shown in the ADT Book (Traffic Flow Maps) and the Traffic Maps.
Question: What is the mechanism that we have to convert short duration counts into accurate estimates of annual conditions? What adjustment has been made to annual conditions to computer AADT from the short duration counts? Are the short duration counts over 48-hour periods or 24-hour period? What is the range of standard deviations of 24-hour monitoring period (e.g. 2 to 25 percent of variability)? Are there documentations on concerning these data (latest documentation in electronic format)? For example, methodology of calculating the seasonal and Day-of-Week adjustment factors from Automatic Traffic Recorder (ATR) data?
Traffic Variation factors Derived from the continuous ATR stations. Based on five year averages TDOT is currently working to expand ATR stations and create more precise variation factors.
Traffic Variation Factors (TVF) Purpose: Adjustment of the raw short period counts Explanations: ATR stations are stratified into four functional group Day of the week and month of the year factors are calculated for each functional group These factors are averaged with previous four years factors (Extremely high or low factors are deleted) The factors are rounded to two decimal places and presented in the table form 2003 Monthly Variation Factors by Day of Week January February Rural Interstate Sun 1.31 1.24 Mon 1.28 1.23 Tue 1.23 1.20 Wed 1.23 1.17 Thu 1.23 1.11 Fri 1.21 1.04 Sat 1.18 1.17 Rural Other Urban Recreational
Variation Factors
Axle-Correction Factor Based on a Machine/Manual Classification Count. The Axle-correction factor is required to adjust for multiple axles. The counters count axles, not vehicles. Axle inflation and over-count error are due to the way the road tube counter operates.
O Anderson County Traffic Map
Machine Classification Count Axle-Correction Factor Truck percentage (Combination of Single Unit & Multi Unit) 65,751 51,615 / 65,751 0.785
This Coverage Count report from ADAM shows 24 hour data for Station Number 84 in Anderson County
Trend Analysis: In the boxes under Enter range of years for forecasting AADT, enter the range of years you would need a forecast. Then choose the Run Analysis button. In this example, you get a Yearly Growth Factor of +0.299% per year or 1% as a minimum. (See Slide Number 14 for explanation.)
In this example, the graph shows two peak years (1986 & 1995). You may want to exclude these two peaks. To do that, enter the years you want to exclude in the box labeled Excluding: Then choose the Trend Analysis button.
By excluding these two years, you now get a different Yearly Growth Factor, which is now 1.717%.
Care should be exercised when receiving a negative growth rate. TDOT suggests that you should use caution when a Yearly Growth Factor is less than 1%. You should either use, as a minimum, a 1% growth rate or go back to the Enter Years to be used for Regression Model and enter a range or a start year where it looks like the yearly counts are increasing.
While you are on this screen, if you want to see the Yearly Growth Factor for the entire County by total and by type, choose the Detailed Growth button.
Starting in the year 2003 (for some counts in 2002), count information within ADAM contains 15-minute counts. Therefore, peak hour volumes and factors could be derived. This information is displayed, when available.
24-Hour Data: To see the hourly totals for each of the 24 hours choose the 24-Hour Data button in the lower right-hand corner.
24-Hour Data:
The ADAM version (Oracle) of the database, stored on TDOT s servers, contains a Map link. Also, on the Trend Data screen there is a button labeled Select by Query (a map function). To obtain the Station Number of the location where you need information, the ADT Book (Traffic Flow Maps) for the year 2003 now contain the majority of these numbers. Traffic maps containing all of the station numbers can be found in the Traffic Statistics Section in the Traffic Planning and Statistics Office of the Planning Division. The Internet has maps showing all of the Traffic Count Station Numbers.
ADAM now houses historical records of approximately 14,500 annual cycle traffic counts and 886 ramp traffic counts, dating back to the year 1985. ADAM is an evolving database. The database will continue to contain all the cycle counts and ramp counts updated yearly, but will hopefully in the near future also contain modules for all the Automatic Traffic Recorders (ATR), Weigh-in-Motion (WIM), Classification and Structure counts.
ATR Locations
Question: How do you determine the appropriate number of continuous ATR locations? How many ATR s are in each group (e.g. Interstate Rural etc.)? Do we have ATR data from several stations and different roadway functional classifications?
Question: Do we use the AADT from the ATRs for the sections where the permanent ATR are located? Answer: No, a cycle count is used at each ATR site.
ATR Station Description
ADAM: ATR Information
ADAM: Continuous ATR Monthly Summary
Question: What is the limitation of vehicle automatic vehicle classifiers? What is our state's classification procedure? How are the data collected and summarized? Are the vehicle classification count data by location, by functional classification, by day and by hour? Are the collector and local classes counted? Are Friday, Saturday, and Sundays counted? Etc. etc...
Question: TN does have a continuous classification count program, correct? Answer: Yes, approximately 600 classification count locations are performed on a three year rotating basis.
Question: Where are these continuous classification count stations located?
CLASSIFICATION PROGRAM RURAL 1- INTERSTATE: 40 2- PRINCIPAL ARTERIAL: 65 6- MINOR ARTERIAL: 153 7- MAJOR COLLECTOR: 35 8- MINOR COLLECTOR: 13 TOTALS: 306 URBAN 11- INTERSTATE: 54 12- PRINCIPAL ARTERIAL: 11 14- MINOR ARTERIAL: 105 16- MAJOR COLLECTOR: 101 17- MINOR COLLECTOR: 7 19- LOCAL: 1 TOTALS: 279
Question: How are these locations determined? Answer: FHWA statistical sampling. Being reviewed and adjusted. Over 1,000 on state routes and nearly 1400 lower classified routes will have classification counts performed.
Question: What types of vehicle classification collection equipment do you use to collect these data? Answer: Diamond Unicorn Counters using dual loops are utilized at sites up to two lanes each direction. 24-hour manual counts are derived on 3+ lanes each direction.
Question: How often do we calibrate, test and validate the performance of its classification equipment? Answer: Each counter is visually inspected by the operator at the time of installation. If problems occur, either in house or factory repairs are performed.
Weigh in Motion/Classification Station Description
Viewing Vehicle Classification information
Weigh-in-Motion Data
Question: What is the range of differences between a mainline volume estimate for the section ending at the end anchor point and the volume computed from data collected at that anchor point? How are the differences handled? Answer: Each anchor point is reviewed for statistical accuracy at a maximum of 15%
Question: How do you reconcile of ramp counts to anchor points when using ramp counts to estimate mainline interstate volume? Answer: Manual adjustments to individual ramp counts exceeding allowable percentages are performed.
Ramp Stations
Ramp Calibration
ADT Book on the Internet
Traffic History on the Internet
Traffic History on the Internet
Question: I have several general questions regarding the HPMS reporting methodology and how the state functional classification system is determined. I think that it would be good to just get a general overview of the methodology that is used to derive the HPMS numbers and also what the process for updating the state functional classification system is.
Question: What statistical sampling method is used for the road that are not NHS and other principal arterial; and local roads?
HPMS (Highway Performance Monitoring System) The Highway Performance Monitoring System (HPMS) provides data that reflects the extent, condition, performance, use and operating characteristics of the nation s highways Length, lane-mile, and travel data are used for apportionment of Federal-aid highway funds under the Transportation Equity Act for the 21 st century HPMS data are also used for assessing and reporting highway system performance under FHWA s strategic planning process HPMS data form the basis of the analyses that support the Condition and Performance reports to congress HPMS data are the primary source for a substantial portion of the information published in Highway Statistics and other FHWA publications and media HPMS data are widely used throughout the transportation community, including other governmental interests, business and industry, institutions of higher learning, the media and the general public
HPMS contains a mix of universe and sample data for arterial and collector functional systems. Limited information on travel and paved miles is included in summary form for the lowest functional systems Roads are classified as to their functional usage. These functional classifications include Interstates, Other Urban Freeways, Principal Arterials, Minor Arterials, Collectors and Local Roads The Rural Functional Classification System is assigned by TDOT s Systems Planning Section. The Urban Functional Classification System is assigned by the individual Small Urban and Urbanized Areas (MPO s) Traffic for the Local functional system is derived from a sampling of counts done at local bridges for the National Bridge Inventory. As more bridges are counted, these estimates will improve HPMS requires a 5-10 percent sample in rural areas and a 10% sample in urban areas The Universe (100% sample) part of HPMS contains general information about the roadway; length, number of lanes, ADT, Functional Class, Ownership The Sample part of HPMS contains more detailed information; Pavement Type, Lane Width, Shoulder Type and Width, Capacity and other information Tennessee uses 100% coverage of traffic data for the arterial and collector functional systems Vehicles are counted on roadway segments to calculate the Average Daily Traffic Daily Vehicle Miles of Travel (DVMT) is calculated for each section of roadway by multiplying the Average Daily Traffic (ADT) by the length of the segment HPMS data is used to produce reports of mileage and travel (DVMT) for Rural, individual Urban Areas and statewide by functional system Traffic data can be combined with other information (such as number of lanes) to provide other reports The traffic data for the local functional system is derived from a sampling procedure The HPMS report is produced each year to represent the state s public road system as of December 31 of that year The HPMS report is to be submitted to FHWA by June 15 of the next year
Functional Classification Process The Functional Classification System (FC) is updated two ways; each way dependent on the requesting city being a Large Urban Area or a Small Urban Area. A Small Urban Area may request a change, explain the change, and provide a map in a letter from the mayor. This request is then evaluated by Systems Planning to see if the requirements are met. Each city, regardless if it is large or small, has a percentage of its roads that can be classified. These percentages are established by the Federal Highway Administration. If the percentages are within limits, the section of roadway must meet requirements such as tying into other FC roads and meeting minimum requirements. If the change would put the percentages out of balance a meeting is conducted with the city to remove already classified roads from the system, providing room for the additions. Once these requirements are met, a letter is prepared authorizing the change and published. The FC map is then changed to reflect the revision. For a Small Urban Area, a letter is sent to the Tennessee Regional Development District for delivery to the requesting city. A Large Urban Area would be incorporated into a Metropolitan Planning Organization (MPO). Smaller cities may also be incorporated into the MPO as well (Springfield and Smyrna in Nashville MPO). The request is made through the MPO and comes in the form of a resolution from the MPO Executive Board requesting the change. The same process occurs as happens in the Small Urban Area request. Percentages must be met, road sections must connect, and roads must meet minimum requirements. Upon meeting the requirements, a letter is prepared and published and sent to the MPO. The map is then changed to show the revisions. Should the road sections not meet the minimum requirements, meetings are conducted with the city/mpo and any problems are resolved.
Urbanized Areas - MPO Discuss any revisions to the functional classification system with Joe Armstrong or Rusty Staggs before approval by the TCC or the Executive Board. This will insure that all guidelines are met prior to official approval. Any route added as an urban arterial should connect to an equal or higher classified route with the exception of routes entering or leaving the urbanized area boundary. Urban arterials cannot exceed 15% of the total miles within the urbanized area. Any route added as an urban collector should connect to an equal or higher classified route with the exception of routes entering or leaving the urbanized area boundary. Urban collectors cannot exceed 10% of the total miles within the urbanized area. Any functional classification revision has to be approved by the Executive Board with a signed resolution and map. All projects listed in the TIP should be functionally classified.
Small Urban Areas Discuss any revisions to the functional classification system with Joe Armstrong or Rusty Staggs before submitting request. This will insure that all guidelines are met prior to official approval. Any revision has to be requested by letter from the Mayor with a route description, and map. Letters can be submitted to Jeanne Stevens, Rusty Staggs, or Joe Armstrong. Any route added as an urban arterial should connect to an equal or higher classified route with the exception of routes entering or leaving the urban boundary. Urban arterials cannot exceed 15% of the total miles within the urban area. Any route added as an urban collector should connect to an equal or higher classified route with the exception of routes entering or leaving the urban boundary. Urban collectors cannot exceed 10% of the total miles within the urban area. Projects have to be classified before federal funds can be spent.
Safety Planning Determines the Linear Reference System Locations for Crashes on Interstates, State Highways, and Functionally Classified Routes Prepares Crash Data Reports for Problem Identification and Project Development Prepares a list of Potential Projects for the Hazard Elimination Safety Program Develops Quarterly and Annual Speed Summary Reports for the Tennessee Speed Monitoring Program
Safety Planning Section analyzes approximately 200,000 Crash Reports per year to determine the LRS Location Crash Report
Crash Data Reports may include any or all of the following: Crash Records Listing Crash Summary Report Crash Rate Analyses Collision Diagram Copies of Officer s Crash Reports
Requested by Nashville MPO Crash Data Request Form
Crash Records Listing
Crash Summary Report
Collision Diagram
Hazard Elimination Safety Program List of potential safety projects Statewide average rates Prepared ever two years. This and all other crash data is protected by Section 409 USC. Any request from outside of TDOT must be made through our legal division. The data cannot be used for any court action
Average Crash Rates
Intersection Average Crash Rates
Speed Monitoring Program Monitoring of Interstate and other routes with Speed Limits of 55MPH or greater. Reports prepared quearterly and annually Submitted to FHWA, with copies provided to TDOS and GHSO
Speed Summary Report
Question: Since we will soon have our own freeway ITS system in place here in Knoxville, I would like to know if the data that will be collected from the radar units will be archived/summarized into a useful format for planning purposes. Also, what types of data can be collected accurately from the technologies being deployed and how can they be used to derive other information such as congestion indices?
Question: One specific issue that has come up in Knox County is with the amount of VMT that is being reported on the Urban Local classification in the HPMS estimates, which is apparently the highest in the entire state surpassing both Shelby and Davidson counties. My understanding is that Dr. Han has developed the methodology for coming up with local VMT and it would be good to hear what that entails.
Local Road DVMT Estimation Prepared for Steve Allen 11.29.2004
Challenges No state has extensive count program for local roads due to resource limitations. Every state is require to report local road traffic information annually in its HPMS program.
General Estimation Model (GEM) An estimation model was developed based on: Previous studies Special bridge counts on local roads Historical estimation Statistical relationship between traffic on local roads and other roadways Growth trend in each county Rural/urban designation of the roads
Model Development Historical Data Special/Bridge Counts ADT/VMT on All Roadways Growth Trends Other Information Statistical Analyses Covariance of variables Time series analysis Step-wise regression Etc. General Estimation Model
Key GEM Parameters Rural Minor Collector AADT Urban Collector AADT Bridge & Special Count AADT Growth Rate for Each County Mileages of Various Roadways
GEM Procedure For each county 1. Calculate Bridge ADT for Target Year 2. Calculate Rural Local ADT 3. Calculate Urban Local ADT 4. Calculate DVMT for Rural and Urban Local Roads 5. Calculate County-wide DVMT 6. Recalibrate of Equations Frequently
Sample Spreadsheet
Details of the GEM Procedure Appendix
Complete List of Variables Year n (GIVEN) R 3 is rural minor collector AADT for year n (GIVEN) U 3 is urban collector AADT for year n (GIVEN) X 5 is bridge AADT mean for year n X 5OLD is old bridge AADT mean from year m L R is rural local road ADT for a county L U is urban local road ADT for a county L T is total local road ADT for a county G n-m is the local county growth rate for year n-m (GIVEN) M R is the mileage of rural local roads in a county (GIVEN) M U is the mileage of urban local roads in a county (GIVEN) DVMT R is rural DVMT for a county DVMT U is urban DVMT for a county DVMT is total DVMT for a county
GEM Step 1 Find the most recent bridge data for the county X 5OLD = Average of all bridge ADT counts in the county If the data is for year n then X 5 = X 5OLD Otherwise if the data is from m years before year n, then X 5 = (1+G n-1 )(1+G n-2 ) (1+G n-m )X 5OLD
GEM Step 2 If there is no bridge data for the county: L R = 7.344 + 0.214 R 3 If there is bridge data for the county: L R = 9.086 + 0.168 R 3 + 0.0547 X 5 Note: Equations should be derived individually for each state and locale.
GEM Step 3 If there is no bridge data for the county: L U = 14.973 + 0.231 U 3 If there is bridge data for the county: L U = 18.550 + 0.203 U 3 + 0.0911 X 5 Note: Equations should be derived individually for each state and locale.
GEM Step 4 DVMT R = M R L R DVMT U = M U L U DVMT = DVMT R + DVMT U
L T = DVMT/(M R + M U ) GEM Step 5
GEM Step 6 Statistical results, while representative of the whole, may be off at individual locales. Adjustment based on local knowledge and engineering judgment should be made over time to assure quality results of the model.
Question Why is Knox County s estimated urban local road VMT the highest in TN surpassing Shelby and Davidson counties? Is there something wrong with the estimation?
Knox Co. High Urban Local DVMT Prepared for Steve Allen 11.30.2004
Top 370 Urban Areas Local/Total VMT Ratios 35 30 25 20 15 Shelby Hamilton Davidson Knox 10 5 0 0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50% Local Road VMT/Total Road VMT
Observation While Knox County s (Urban Local VMT)/(Total Urban VMT) ratio (about 18%) is higher than other Tennessee urban areas, there are plenty of urban areas with higher, and some much higher, ratios.
Top 370 Urban Areas Local/Total Miles Ratios 70 60 50 Shelby Hamilton Davidson 40 30 Knox 20 10 0 50% 60% 70% 80% 90% 100% Local Road Miles/Total Road Miles
Observation Knox County has a much higher percentage of its total roadway mileages being local roads than all other Tennessee urban areas and over 98% of the Top 370 US urban areas! The mileages of roadways are NOT estimated by statistical models but reported by TDOT. Perhaps a good portion of these local roads should have been designated as higher-class roads.
Discussions The 4-year Knox Co. Local Road VMT trend is not out of the order DVMT 2,263,730 2,320,559 2,327,449 2,597,464 Mileage 1,355 1,358 1,361 1,361 The General Estimation Model is a statistical model and, hence, may not always be on the mark for all 95 counties all the time. Even though Knox Co. VMT appear to be reasonable by comparison, engineering judgment may be used to calibrate the model if necessary.
Are there any questions?