Highway Performance Monitoring System
|The HPMS is an integrated database covering all public mileage within the state. The state delivers it to the Federal Highway Administration (FHWA) by June 15 of each year. The June submittal covers data for the previous calendar year. Thus, the June 1996 submittal was data as of December 31, 1995. This submittal includes Oregon´s certified mileage for the year. This is ODOT´s official tally of public mileage and a special letter indicating mileage on Indian Reservations.|
All mileage is included in some record in the database. ODOT queries all jurisdictions each year to obtain the latest breakdowns of their mileage. The sum is referred to as our universe. Because it is impracticable to collect all data items on all the universe, the HPMS contains samples. We pick the samples for various functional classes of the universe to give a representation of those classes. Universe records require a limited amount of data. We currently report 82 data items for the samples.
The sampling process allows ODOT to gather data on a limited number of samples, but still represent the entire universe. We currently have over 2200 samples. The freeways are completely sampled. Samples on other classes have expansion factors. These factors represent the ratio of universe mileage to sample mileage for a category of roads. When the data from samples is expanded, it provides us the chance to create summaries of data about various road systems. Important data on the samples include traffic, pavement, and inventory data. The data from HPMS is used by Congress and locally to assess the state of our road system. It is a portion of the federal aid allocation process.
|There are quite a few data items covering identification of the segment and the systems to which it belongs. The systems recorded for each segment are:|
Rural / Urban Designation: This is the geographic code for a segment being rural, small urban, urbanized, or urbanized over 200,000 population. If the section is in an urbanized area, we include a code indicating which urban area.
Functional classification (FC): The rural classifications are: Interstate, Other Principal Arterial, Minor Arterial, Major Collector, Minor Collector, or Local. The urban classifications are: Interstate, Other Freeways and Expressways, Other Principal Arterial, Minor Arterial, Collector, or Local. For many data items, FC is the basis for whether the item is required or not. For instance, an adequacy rating may be substituted for curve information on paved rural major collectors.
National Highway System (NHS): A road section is coded as NHS or not. The FHWA confirms the roads congress approves as NHS. For 1996 data reported in 1997, those roads which are intermodal connectors will have codes to indicate what type of intermodal facility they reach.
Route signing: Route signing on samples is tracked for interstate, U.S., Oregon, county, and forest service routes.
Jurisdiction: This code gives the level of ownership for the road. HPMS must include roads of all public entities, whether state, county, city, federal, or several other possibilities. State and federal are broken into several sub-categories.
Special Systems: There are several special categories of interstate, as well as the Strategic Highway Network, Indian Reservation Roads, National Forest Highways, and National Park Roads.
Designated Truck Route / Parkway: The federal register listed which routes within the state are designated as truck routes. Another code indicates a road is designated a truck route by the state. Those sections which are not truck routes are coded for being a parkway or not.
A couple of supplemental items added in the 1993 modifications indicate different ways of handling High Occupancy Vehicles (HOV) and varying types of Surveillance Systems.
The table below shows the State of Oregon’s Certified Public Mileage since 1979. The Federal Highway Administration defines a public road as: “Roads under the jurisdiction of and maintained by a public authority which are open to travel by 2 wheel drive passenger vehicles” (paraphrased). 23 U.S.C. 315, 402(c). The drop in mileage between 1984 and 1985 is primarily due to the U.S. Forest Service closing many miles of their roads to the public. The drop in mileage between 1993 and 1994 was due for the most part to a change in BLM mileage being reported. Most of the drop in mileage between 2006 and 2007 is due to a change in reported mileage from the Oregon State Forest Service and the US Forest Service. The 2000 to current mileage does not include BLM mileage as per a federal ruling.
The FHWA gives each state and territory eight spreadsheet templates to complete with the year´s summary data. Here is the list of templates:
1. System Length and Daily Travel
There are statewide totals for population, net land area, length, and travel. The travel is expressed in daily vehicle kilometers of travel (dvkt). The state is then broken into three sub-areas. These are rural, small urban, and urbanized. These areas are delimited by FHWA´s transportation urban boundaries. Urbanized are areas of 50,000 population or more. Small urban is the 5,000 to 50,000 population range. Rural is everything that is left over, whether in a small city or the middle of nowhere. Each of these three sub-areas have totals for population; land area; and then length and dvkt by functional classification.
2. System Length and Daily Vehicle Travel (Urbanized)
Each urbanized area is detailed on template 2. Oregon has seven urbanized areas. They are Portland-Metro, Salem-Keizer, Eugene-Springfield, Medford-Central Point, Bend, Corvallis and Rainier. Rainier is included because it is a part of the Longview, Washington urbanized area. The state supplies a population and land area total for each of these areas. We also supply length, travel, and occupancy for each functional classification in each area. The occupancy data is derived from the state´s accident records.
3. System Length and Daily Vehicle Travel (NAAQS)
The third template is like the second except that it is for areas not meeting certain standards of the National Ambient Air Quality Standards. Currently, Oregon has no areas far enough out of attainment to fall within this category.
4. Minor Collector and Local Functional System Length
The state estimates length within the local and minor collector classes split among surface types and volume groups.
5. Fatal and Injury Motor Vehicle Accidents
For each functional classification, the state tallies length; travel; fatal and injury accidents; fatally injured and injured persons; and fatally injured and injured pedestrians.
6. Travel Activity by Vehicle Type (Basic Data)
The state estimates percentages of vehicles in each of FHWA´s thirteen vehicle classes for each functional classification. These estimates are derived from approximately three hundred vehicle class counts performed on a three year schedule.
7. Travel Activity by Vehicle Type (Supplemental Data)
This template is used to indicate which days of the week, months of the year, and hours of the day are used for template 6 data. Any other comments on combining classes or special considerations are also reported here. Oregon uses only weekday counts, mostly March through October. We use 24-hour manual counts or 48-hour machine counts.
8. U.S. Territory Information
Oregon is no longer a territory as of February 14, 1859. Therefore, we ignore this template.
Traffic data is one of the most crucial elements of the HPMS. The data is used to gauge use of the system and individual samples.
ODOT produces Daily Vehicle Kilometers of Travel (DVKT) values for each functional classification (FC) of roadway within each of the seven geographic summary areas that we cover. For other customers the travel data is available as Daily Vehicle Miles of Travel (DVMT). We report percentage of travel within each of FHWA´s thirteen vehicle classes by FC. The urbanized area summary includes vehicle occupancy data for each urbanized area, by FC. Starting with 1996, ODOT uses accident data to produce these vehicle occupancy rates. This is the average number of persons in the vehicle for cars, buses, and light trucks. We use an average of data from the last three years.
The most basic traffic data element is the Annual Average Daily Traffic (AADT). We derive most of the AADTs from 48-hour road tube counters. Each sample is counted on a three year cycle. The Future AADT is the product of the AADT and a growth factor. The Metropolitan Planning Organizations (MPOs) supply the growth factors for the seven urbanized areas, in accordance with federal regulations. This is output from their modeling efforts. Analysis of the past AADTs provides the growth rates for all other samples.
Analysis of future needs includes looking at roads at or near capacity. Some of the data needed to compute the capacities include: K Factors (percent of AADT at the 30th highest hour), D Factors (percent of traffic in the peak direction at peak time), percent trucks (both daily and peak time), available turning bays, posted speed, signals, percentage green time, and number and type of intersections. Lane width, number of lanes, and available shoulder also help determine how comfortable drivers will feel driving a section of road. Beginning with the June 1996 submittal we compute the capacities using the 1994 Highway Capacity Manual. After computing the capacities, HPMS software computes a Volume/Service Flow ratio (V/SF).
ODOT has three basic sources of traffic data.
The most commonly used is a road tube counter. We have a variety of machine types from simple machines that give only a total volume to classifiers that can give the vehicle types by time period.
Where road tubes are not practicable for collecting vehicle class data, people will watch the road and tally the vehicle types. The volume on many freeway counts is too heavy to stick tubes out, so these class counts are almost exclusively done manually. Turning movement studies are also a manual effort, though not used in HPMS.
Our Automatic Traffic Recorders (ATR´s) are permanent installations with loops in the pavement. Just recently, ODOT began pulling data from signals. The ATR´s are the only machines that record long enough to obtain K Factors. ODOT has 119 ATR´s, including two signal setups.
The HPMS sample data includes data to support analysis of a state´s pavement condition or special studies about pavement on the local or national scale.
Pavement data included:
International Roughness Index (IRI): is required on all principal arterials, NHS, and Intermodal connectors. Also required on minor arterial samples. This item was not required until the modifications to the HPMS field manual in 1993.
Pavement Condition, or Present Serviceability Rating (PSR): required for all paved samples not requiring an IRI measurement.
Surface/Pavement Type: indicates whether the sample is dirt, gravel, brick, asphalt, or concrete, or some further breakdown of these types.
Pavement Section: indicates heavy, medium, or light pavement, or if depth or structural number is known. Only required for principal arterials.
Structural Number (SN) or Depth (D): SN is calculated if the profile of the section is known for an asphalt sample. D is the measurement of the depth of a concrete sample. Only required for principal arterials.
Type of Base: This is the type of material used as base. Only required for principal arterials.
Type of subgrade: indicates if subgrade is coarse or fine material. Only required for principal arterials.
Overlay or Pavement Structure Thickness: Pavement thickness is reported for new pavements and overlay thickness is reported for overlays.
Improvements are often coded at the same time as changes in the pavement data.
Climate Zone: This is a code tied to the county code. There are nine different combinations of the three wet/dry conditions and three winter conditions. From the mild, wet conditions of NW Oregon to the dry, harsh conditions of SE Oregon, our state has plenty of variety.
Drainage Adequacy: A code indicates good, fair, or poor drainage.
The HPMS dataset is intended as a current inventory of road system conditions within the state. As it is updated, it also sheds light on improvements to the system. In addition to changes in inventory data, the sample data contains specific fields to track what improvements are accomplished. There are codes for improvement types, thickness, and year. Pavement type, structure, and base type might require changes. Lane configurations, pavement condition, turn bays, and many other items could change as a result of overlays or more extensive reconstruction.
The HPMS samples are inventoried on a three year schedule. Teams go each year to selected counties gathering information across and along each sample. Typical samples are between 0.3 and 10.0 miles long in rural areas, and between 0.1 and 3.0 miles long in urban areas. Staff members measure lanes, medians, and shoulders. We check pavement type and condition. We note parking, intersections, speed signing and signalization. Some changes signal the need to report improvements. FHWA supplies a field manual showing how to code the data collected. The field trips are often the only way for state staff to find out about changes on other jurisdiction´s roads, such as changing from one-way to two-way. On occasion HPMS staff will take pictures of non-state samples. ODOT produces videos of all state highways. This helps our memories if we find a data conflict once we are back at the office.