Section 2: Data File Creation/Maintenance

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Texas Reference Marker

The Texas Reference Marker (TRM) system is an automated system that documents the past, present, and future state-maintained highway network. It contains all physical features on the state highway system such as signs, culverts, and intersections. Markers, similar to mileposts, are installed at various locations along state highways and are numbered relative to the statewide TRM grid. Physical features are referenced to the markers in terms of mileage displacement from the nearest marker.

Data Collection. TRM accomplished analyzing preliminary and final construction plans from the General Services Division. DMS staff reviews these plans to determine if any specific project is going to affect the highway network mileage or design. Staff determines if any other administrative functions of TRM will be affected. This investigation includes reviewing city maps, functional classification maps, or any other map source that correctly depicts approved administrative data.

All functions of the TRM system are conducted in headquarters or district offices, with the exception of ad-hoc reviews. In these cases, field crews are sent to check specific physical features of a highway. Staff enters data at computer terminals using codes such as those related to the Highway Performance Monitoring System (HPMS).

The TRM section in each district helps maintain the TRM files, primarily related to surface elements of the highways. The TRM section within TPP is responsible for maintaining the highway network and administrative data required for HPMS.

DMS staff assists the district offices with requests for changes to the state highway network by preparing Minute Orders for approval by the Texas Transportation Commission. The staff secures concurrences from Traffic Operations and Design Divisions for each change request. All districts and divisions are notified of Commission-approved changes.

TRM is a major link to the state highway system geographic information system (GIS), particularly related to distance from origin (DFO) data.

Mile Point Reference Marker Equivalency. The Mile Point Reference Marker Equivalency (MPRME) file was developed as a conversion tool to allow cross-reference and data reporting from TRM and from files keyed on control-section-milepoints. The MPRME file matches reference markers and control-section-milepoint data.

  • Data Source: TRM is the source for reference marker locations for MPRME, and the Roadway Inventory (RI) file is the source for control-section-milepoint locations.
  • Data Update: The MPRME file is created from TRM and RI data on a monthly cycle.
  • Load to RIS: The MPRME file is loaded to the Roadway Information System, commonly referred to as the RIS, on a monthly basis.
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State Railroad File

The State Railroad File is a current, active list of only open, on-system railroad crossings. This is an in-house TxDOT file, created and updated solely by TxDOT staff. TxDOT has control over this file, making it an accurate file; therefore, TxDOT has a high degree of confidence in it.

Data Reception. Private railroads, the Traffic Operations Division, and TxDOT districts provide the State Railroad File data to DMS.

Update Files In-house. Data Management Section staff updates the State Railroad File in-house, using data provided by the various sources.

Roadway Information System. The RIS provides mainframe computer access for districts and divisions.

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RI File

The RI file consists of six subfiles of roadway information and is maintained by update transactions. This information is keyed by control-section and beginning milepoint. Following is a list of the subfiles and the type of information each contains:

  • Subfile 1 - On-system roadways which are either state-maintained (equates to TRM) or under local maintenance. MPRME is the tie between control-section-milepoint and reference marker.
  • Subfile 2 - County roads
  • Subfile 3 - Functionally classified city streets
  • Subfile 4 - Unclassified city streets
  • Subfile 8 - Frontage roads: created from TRM using MPRME to convert reference marker to control-section-milepoint data. Traffic on these roads travels in ascending reference marker direction.
  • Subfile 9 - Frontage roads on which traffic travels in descending reference marker direction

DMS has a goal to have all city streets in one file. It will accomplish this goal through the future city street inventory project.

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Accident File

Data for the Accident File originate from the Texas Department of Public Safety (DPS) via mainframe computer cartridge tapes. DMS staff runs the data against the RI to update the milepoints. A report is given back to DPS with documentation of mismatched data.

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Highway Performance Monitoring System

The Highway Performance Monitoring System (HPMS) is a federally mandated data reporting system providing roadway/traffic data to the Federal Highway Administration (FHWA) from TxDOT. The HPMS data are vital to TxDOT as these data influence federal apportionments to the state. Roadway mileages and vehicle miles traveled (VMT) are directly related to the apportionment formulas. Part of the federal funding distribution formula is based on traffic volumes reported by HPMS. Therefore, the ability to program and develop projects is related to HPMS.

While the HPMS may have the appearance of a database, it is actually a file comprised of data from various TxDOT databases. HPMS is created from the RI files, TRM, and the pavement management information system (PMIS). TxDOT divisions and districts update these databases in order to provide the most current data available. The HPMS submittal reflects the state data as of December 31 each year. DMS performs the update at the end of each calendar year by taking a computer tape template and reading in new RI data. This timing is dependent upon receiving some data elements from TxDOT districts, other sections within TPP, and other divisions.

DMS updates TRM and RI reports year-round. The December 31 data set is a snapshot of files taken after the final updates are made. During a four-month processing period, the Traffic Section applies its most current data (traffic data file, ADT design data, percent trucks, etc.) and PMIS (IRI - a roughness index for road surface that develops a score to rate the condition of the road). The Traffic Section takes the tape and enters the data. This process follows the year-end update. The final HPMS version is due each year to FHWA by June 15.

The Data Management Section is responsible to FHWA for certifying the public road mileage. This certification reports the total public road mileages (on and off the state highway system) as a part of the HPMS requirements.

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HPMS Mileage Certification

  • On-system - certified through districts
  • County roads - recently inventoried to validate data; in future years, counties will advise DMS of new or closed roads and DMS will verify using distance measuring instruments (DMIs) and a global positioning system (GPS), then input the data into electronic files
  • City streets - will be validated and treated similarly to county roads.
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Linear Reference System

The Linear Reference System (LRS) accompanies the HPMS report and is required by FHWA, who provides the computer software. LRS identifies a network of roads by functional classification. The goal is to identify all HPMS data collection sites by functional classification. In rural areas this system identifies roads functionally classified as “major collector” and above. LRS identifies roads in urban areas with functional classifications of “principal arterial” and higher. Staff assigns nodes to break points, such as intersections and county lines, along roads.

Data Collection. The majority of the data collection necessary to support LRS comes from district offices. The districts notify DMS when an off-system road becomes part of the statewide system, when a new on-system facility is opened to the public, or when an on-system road’s functional classification changes. These changes require modifications to the subfile designation and/or location attributes.

Contractors and DMS staff, under the direction of the Data Management Section, collected county road mileage and other data for the County Road Inventory Project (CRIP). DMS crews provided quality control by inspecting the work. Section staff was responsible for checking the accuracy of county road inventory data to ensure that mileages were reported accurately. County road mileages are updated annually by the counties through official mileage certifications.

Data Users. There are several users of the CRIP database. The State Comptroller’s Office uses the information to disburse the Lateral Road and Bridge Fund. TxDOT Vehicle Title and Registration Division distributes funds to counties according to mileages recorded for each county. Budget and Finance Division calculates overweight permit fees using the county road inventory. Bridge Division assigns bridge structure identifications in its BRINSAP database using county road numbers from the inventory. Other data users include the Information Systems Division (related to GIS issues), county 911 coordinators, county officials (such as judges and commissioners), and the Texas Transportation Commission (for Minute Orders designating new highways and highway relocations).

The Data Management Section is responsible for the certification of county road mileage (off-system only) to the State Comptroller. This information is used for dispensing funds from the Lateral Road and Bridge Fund, which consists of approximately $7.3 million each year. This information is also used for dispensing a portion of the fees collected from overweight permits, vehicle titles, and vehicle registrations.

TT Tables. DMS publishes TT Tables annually and places them on the online document viewing system (ODVS) as a status report of the state highway system. The ODVS is available to all departmental users and contains such information as mileage, vehicle miles, lane miles, etc.

Ad Hoc Reports. The Data Management Section receives requests for data from the general public, the TxDOT Public Information Office, the Legislature, and other agencies or individuals. Data Management staff uses its databases to respond to these inquiries. Staff prioritizes responses and routine work based on the urgency of data requests.

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