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Frequently Asked Questions
 Working on it...
Application
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“Introduction to LTPP InfoPave” video in the home page provides a quick overview of LTPP InfoPave. The "How To…" section in the "Help" module in the navigation bar contains videos that will give an overview of the LTPP program as well as explain the many facets of LTPP InfoPave related to searching, viewing, and accessing LTPP data.
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No. The public data release through Standard Data Release (SDR) is only a part of the LTPP data resources.
With LTPP InfoPave, users are provided meaningful and easy access to all LTPP data with the supporting technological applications and tools. Unlike the Standard Data Release, the user needs minimal previous exposure to the LTPP data to find a specific data set. Specifically, the pavement performance database included in the SDR is the same as that in InfoPave, but in InfoPave, it is meaningfully organized for the user with user friendly table and field names and the data expanded to section level to facilitate easy data access. In addition, InfoPave provides access to research documents and ancillary information management system (AIMS) data that supplement the Pavement Performance Database (PPDB) data which were never part of the standard data release (SDR) due to space constraints.
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“Introduction to LTPP InfoPave” video in the home page will provide an overview of the data types and multiple means of exploring and accessing the LTPP data.
If you are not familiar with LTPP, a good point to start is with Search in the upper right hand corner of the main screen. Enter a term and click on Go. The Search results will come up with four categories: Library, Data, Ancillary Data and Sections. Clicking the associated button will bring up all items in that category matching the search term. Each category also has additional classifications to subset the data. For example, if you search for “unbonded concrete overlay” under the “Sections” category, you will be able to see all the LTPP sections where an unbonded concrete overlay has been placed. If you click on any of these sections, you will be taken to the “Section Summary Report” where a summary of section location, pavement structure, materials, climate, traffic, and performance is tabulated. Similarly, if you are only looking for LTPP documents and publications related to your search, you can search within the “Reports” category. The search can also be conducted within the Data or Ancillary Data categories to find data corresponding to your keyword.
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To efficiently retrieve a large amount of data from a particular table or tables, use the SQL Export feature listed under the “Data” module. This feature also includes sample SQL codes, which you can modify for your needs. An example SQL statement for selecting all the data from MON_FRICTION table is "SELECT * FROM MON_FRICTION". Due to download size constraints, very large SQL queries such as all data from MON_HSS_PROFILE_SECTION table will not execute. Downloading from LTPP Standard Data Release is recommended to obtain extra-large data sets.
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Once the data is selected and added to data bucket for download using the data selection and download feature, the ‘Data Bucket’ screen provides options such as “Submit Data for Extraction”, “Save”, “Clear”, and “Continue to Data Selection”. Selecting the “Save” option will save the data bucket for extraction later. You can access the saved data buckets (“My Data Buckets”) and downloaded data extractions (“My Data Extractions”) under "under your name". Once you download a data bucket, it will be transferred to the “My Data Extractions” section. My Data Extractions shows the status of each extraction (In Progress or Completed). The completed data extractions can be re-downloaded for up to 7 days. The time to complete the data extraction depends on the data size selected for download and the order in the queue while submitting. You will receive an email notifying the completion of data extraction.
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For easy data subsetting, a predefined filtering system is available within various features of Data and Analysis where data by section can be selected. On the left-hand side of the screen in these features under the “Find Sections” header there are filters for general information, structure, climate, traffic, and performance data that can be used to narrow down the LTPP sections. Scrolling over each filter, displays a description that explains how each filter works. The filter selection applied in one feature will be carried across other features when navigating between them. For example, after selecting the sections that are 25 years old in the Data Section and Download module, you can go to the Analysis module and do a correlation analysis restricted to those sections. As soon as the filtering or selection is applied, the number of LTPP sections shows in the top header.
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LTPP InfoPave helps users to stay connected to LTPP community and meaningfully use LTPP data by means of its various features as briefed below.
The “Customer Support” tab is where you can submit your questions/comments. LTPP InfoPave provides customer support for data and website functionality. If your concerns are related to data, select “Data Support” (addressed through the LTPP customer support services), and if you encounter problems with website functionality, please select “Web Site Support” (addressed through LTPP InfoPave customer services).
The website’s “Help” tab has: “Release Notes” for data release and maintenance updates; “Frequently Asked Questions” which address typical questions for InfoPave; “Presentations” regarding LTPP data; “Application Samples” to show examples of problem statements and how LTPP InfoPave can be used to solve these problems; and “Contact Us” with information about involved personnel and organizations within the LTPP program. Under More on the same tab are “Announcements” to read about LTPP news and “How to …” videos to get started with LTPP InfoPave.
There are many other help resources available through LTPP InfoPave. “LTPP 2014 and Beyond” includes the purpose of LTPP program, the status of LTPP program, information about ongoing features of LTPP, and options to improve the current LTPP program.
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When you access LTPP data by location the options are Map Sections and Map Data Ranges. Map sections shows the location of active (green) and out-of-study (red) sections. Map Data Ranges includes a legend showing the color coding criteria based on the data selection. For example, selecting the pavement age, the legend will indicate what range of age each color represents; yellow might show pavement sections with lower age values. These color codes are displayed in concentric circles on the map. The number at the center shows the count of pavement sections in that area on the map. The color of the circle in the middle represents the minimum data range for the pavements within that group, and the color of the outermost circle indicates the maximum data range for the pavements within that group.
If you zoom in to see a specific pavement section, it will be marked with a balloon shaped pin. The color of this pin represents the status. The circle around the pin represents which range in the data applies to the section.
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Data Pivot feature of LTPP InfoPave provides the dynamic view of LTPP sections displayed as square blocks that are pivoted based on selection (12 currently available) criteria. For example, selecting the climatic region criteria will show the count of sections within each LTPP climatic region. You can also use the filters on the left-hand side in order to further narrow down your search. Each square block in the Pivot view represents a LTPP section. By clicking on a square block, you will be able to see the value of selected parameters and access the Section Summary Report.
Data
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There are two useful tools within InfoPave that can assist you to get an overview of any selected LTPP section. The first one is the “Section Summary Report” which tabulates a summary of section location, pavement structure, materials, climate, traffic, and performance data. The second is the “Section Timeline” which provides an overview of the history of each LTPP section. This timeline includes maintenance and rehabilitation treatments as well as materials testing and performance monitoring activities during the lifetime of LTPP sections. Both of these useful tools are available through the Data module.
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Currently there is no file size limit for download in LTPP InfoPave.
However, the file type may change depending upon the number of records in the selected data bucket. If the number of records is less than 0.5 Million, the data can be downloaded in Excel. If the number of records goes up to 5 Million, it can be downloaded in Access. If the number of records exceeds five million, the data will only be downloaded in SQL files each having up to 10 million records.
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Currently, LTPP InfoPave supports exporting five hundred thousand records in Microsoft Excel and five million records in Microsoft Access. Moreover, when exporting data which exceeds five hundred thousand records, the only download file format available is Microsoft Access format. This constraint is set to limit server resource utilization for data export as well as satisfy the limitation on the number of records supported by Microsoft Excel and Microsoft Access. With this constraint, very large SQL queries (e.g., select * from MON_HSS_PROFILE_ELEVATION_25) will not execute. We recommend downloading LTPP Standard Data Release to obtain extra-large data sets.
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InfoPave provides access to the pavement performance database (PPDB), ancillary information management system (AIMS) data that supplements the PPDB data, and all the LTPP program research documents. The PPDB and AIMS data and the research documents provided through InfoPave is based on the latest Standard Data Release. All data collected under the LTPP program is available through LTPP InfoPave. For any data that you were unable to locate, please submit your request through "Customer Support".
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Even if you are not familiar with LTPP tables, LTPP InfoPave has multiple features (user-friendly data structure, data prioritization, data customization) that help you to find the desired information. Data Selection and Download is the most frequently used feature within LTPP InfoPave, where data is organized for the user to easily gain familiarization with the various data elements in LTPP and access them for download.
After narrowing down (filtering) your search of LTPP sections using “Find Sections”, you can select your desired tables listed under structure, climate, traffic, and performance classes with further applicable sub classes. If you check the option “Show Advanced Data Classification”, additional classes (of lower or lesser priority) will also be displayed. Each sub class might be a single table or group of tables that together contain the information you need. If you hover over each table title, you will see a description of that table. In addition, in accordance with the filters applied to “Find Sections,” it displays the count of sections for which the table has data. While selecting the data, displaying the count of sections allows the user to know if the data is available for all selected sections. With “Show Advanced Data Classification” selected, you can see the list of the fields within each table and customize it to select only those in which you are interested. The downloaded file will include your data individually by each selected tables (Table Names), a separate list of the tables with their descriptions (Table Reference), a table listing all the included fields and their descriptions (Field Reference), and a table listing all other used codes and their descriptions (Codes Reference).
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The frequency of data update will be in accordance with the LTPP data release policy. LTPP InfoPave will be updated for each public data release, which is currently being done annually.
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A .bak file is an export from a MS SQL database. To read the file install a free version of MS SQL Server (Developer or Express).
Open the installed database. If the database was opened MS SQL Server Management Studio after connecting to the instance there should be an entry Databases. If the downloaded LTPP database was not listed as one of the databases under that entry after expansion, it hasn’t been restored yet.
- To restore the database export (*.bak), right click on Databases.
- Select Restore Database.
- Select Device as Source.
- Browse for backup up media type File and add the .bak file location where the LTPP data file was unzipped.
- Click Ok and Ok again.
That should bring the database up in SQL Server. Once it is up, the tables (in Tables) will all have the schema prefix dbo (database owner) and have names like MON_HSS_% for profilometer data. Other LTPP reference tables will be included (Codes, Section_Coordinates, Data Dictionary (LTPPDD)).
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The LTPP program has different levels of data quality (from A through E, where level E data is the highest quality that has passed all the checks). LTPP InfoPave provides access to the same database the LTPP program releases through its Standard Data Release (SDR) which includes data at various levels (A through E). The level of data quality is indicated by the field “Record Status”. The graphics and information displayed on the screens are based on this data.
General
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The LTPP program contains two major experiment types: the General Pavement Studies (GPS) which are comprised of pavement sections constructed before the LTPP program started, and the Specific Pavement Studies (SPS) which are the pavement sections designed and constructed specifically for the LTPP program. Here is a detailed list of the different studies:
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GPS-1: Asphalt Concrete (AC) on Granular Base
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GPS-2: AC on Bound Base
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GPS-3: Jointed Plain Concrete Pavement (JPCP)
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GPS-4: Jointed Reinforced Concrete Pavement (JRCP)
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GPS-5: Continuously Reinforced Concrete Pavement (CRCP)
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GPS-6: AC Overlay of AC Pavement
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GPS-7: AC Overlay of PCC
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GPS-9: Unbonded PCC Overlays on PCC Pavements
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SPS-1: Strategic Study of Structural Factors for Flexible Pavements
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SPS-2: Strategic Study of Structural Factors for Rigid Pavements
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SPS-3: Preventive Maintenance Effectiveness of Flexible Pavements
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SPS-4: Preventive Maintenance Effectiveness of Rigid Pavements
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SPS-5: Rehabilitation of Asphalt Concrete Pavements
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SPS-6: Rehabilitation of Jointed PCC Pavements
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SPS-7: Bonded PCC Overlays on Concrete Pavements
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SPS-8: Study of Environmental Effects in the Absence of Heavy Loads
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SPS-9: Validation of SHRP Asphalt Specification and Mix Design (Superpave)
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SPS-10: Warm Mix Asphalt (WMA) Overlays of AC Pavements
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SPS-11 (Not Initiated): AC Pavement Preservation
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SPS-12 (Not Initiated): PCC Pavement Preservation
Data for studies like Seasonal Monitoring Program (SMP) and Traffic Pool Funded Study (TPFS) were collected on a smaller group of these SPS and GPS sections.
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The “Find Sections” filtering feature in LTPP InfoPave gives users the option to select sections based on experiment type, state/province, etc. This filtering is available in various features of InfoPave where data can be selected at the section level. While using those features, you will be able to apply the “Experiment Type” to define the GPS or SPS experiment and “Location” filters to select the required State/Province.
If you are trying to determine the experiment type of a specific section, you can select the “Section Summary Report” under Data and the experiment number is available in the general information header of the report.
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The unique identifier for LTPP section consists of a combination of STATE_CODE (2 characters)-SHRP_ID (4 characters) (e.g., 27-0501). The naming convention for SHRP_ID varies based on the experiment type as discussed below:
SPS sections SHRP_ID:
The SPS sections have two SHRP_ID systems; the first system is applicable for SPS-1 to SPS-9 projects and the second system is applicable from SPS-10 going forward.
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In the first system, the first character should be 0, A, B, C, etc., depending on how many projects of that type exist in a State (e.g., 0XXX, AXXX, BXXX, etc.). The second character for SPS sites is the experiment number (e.g., 01XX or A1XX for SPS-1 projects consisting of SPS-1 sections). For SPS-3 and SPS-4, the 1st character is always alphabetic starting with A and working through the alphabet depending on the number of projects in a State. For example, SHRP_ID (section ID) A310 means the first project of SPS-3.
There are then additional numbers for sections that were purpose- built for a specific state interest. For example, in the A300 series A310, A320, A330, A340 are all core sections. A311, A321, A341 would all be what are referred to as supplemental sections that were intended to investigate certain features on the sections.
However, a section with a SHRP_ID beginning with a 0 is not always a SPS section. For example, a GPS test section in Texas has a SHRP_ID of 0001. Always check the GPS_SPS field in EXPERIMENT_SECTION table before assuming that a section is an SPS section because of its SHRP_ID.
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In the second system, the first character should be A, B, C, etc., where the character “A” is assigned to the first project and all test sections located on that project. The second character is the experiment number, where “A” is for SPS-10 experiment; “B” is SPS-11, and so on with “Z” representing the SPS-35 experiment. The third and fourth positions indicate project id (00) or SPS experiment designated section id (01 to 58)/ supplemental section id (59-99).
GPS sections SHRP_ID:
There are no naming conventions for GPS experiments.
If you know the STATE_CODE and SHRP_ID, you may use the ‘Section’ search feature or the ‘Find Section’ to locate your LTPP section.
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Construction Number (CONSTRUCTION_NO) is an event number used to relate changes in pavement structure with other time dependent data elements. CN= 1 when a test section is initially accepted into LTPP and is incremented with each change in the layer structure.
For each maintenance and rehabilitation treatment applied to a test section after the start of monitoring under the LTPP program, the CONSTRUCTION_NO (CN) is incremented in the EXPERIMENT_SECTION table. The codes in the CN_CHANGE_REASON field indicate what type of activity was performed to cause the change in CN (For example, a CN_CHANGE_REASON of 19 represents the application of an asphalt concrete overlay). Please see MAINT_WORK codes for the complete code list of CN_CHANGE_REASON. The field CN_ASSIGN_DATE provides a date when the CN event occurred.
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Under Data on the InfoPave website, go to the ‘Section Summary Reports’ and select the State/Province and section SHRP ID number that you have in mind. For example, if you select Vermont from the ‘State’ drop-down menu and 50-1002 from the ‘Section’ drop-down menu, the section overview will tell you that this test section belongs to the GPS-1 experiment, and its coordinates are (44.11961, -73.17939). You will also find that it is located in Addison County on US-7 north bound.
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As all the table, field, and code information is provided along with the downloaded data, it is no longer necessary for the user to search for this data individually.
If the user is interested in getting the table, field, and codes for all tables in PPDB, it is recommended to download the LTPPTD, LTPPDD, and CODES tables that provide this information using the ‘SQL Export’ feature or using ‘SDR Export’ feature in InfoPave.
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In Data Selection and Download, Pavement Structure and Construction select Original Surface construction dates. In any other data export option use the following:
For GPS sections, the INV_AGE.CONSTRUCTION_DATE and INV_AGE.TRAFFIC_OPEN_DATE fields should have the data if state agencies provided the information.
For SPS sections, the SPS_ID.DATE_COMPLETE and SPS_ID.DATE_OPEN_TRAFFIC fields should contain the data if state agencies provided the information.
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U.S. Department of Transportation
Federal Highway Administration
Turner-Fairbank Highway Research Center
6300 Georgetown Pike, HRDI-30
McLean, VA 22101-2296
Tel: 202-493-3068
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Contact LTPP Customer Support Service, ltppinfo@dot.gov, phone: (202) 493-3035, if you cannot locate the supporting documentation.
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No. The LTPP Pavement Performance Data Base (PPDB) has different levels of data quality (from A through E, where level E data is the highest quality that has passed all the checks). This is indicated by the field “Record Status” in each table. The Ancillary Information Management System (AIMS) data is stored based on the guidelines but do not have this quality check associated with it.
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The data files, images, and videos that are part of the LTPP data collection that supplement the Pavement Performance Data Base (PPDB) are called Ancillary Information Management System (AIMS) data. This data is now available for view and download through LTPP InfoPave. The distress images and roadway videos are provided under Visualization. The distress images are also available in ‘Section Timeline’ under Visualization. The data files (such as M&R, FWD and Profile files) are available for download using Ancillary Data Selection and Download under Data.
Pavement Structure and Construction
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The Pavement Cross-Section Viewer under Visualization provides detailed information about the pavement structure of each test section over time. The Pavement Cross-Section Viewer presents layer information in a visual and user-friendly format.
The Section Summary Report under Data also provides layer structure information. In this feature, you will find the layer number, layer type, and layer thickness in the "Representative Pavement Structure” table under Pavement Layer Type and Thickness in the "Pavement Structure and Construction" class under Data Selection and Download.
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Once the sections are selected with ‘Find Sections’ in the ‘Data Selection and Download’ feature, under ‘Structure,’ the tables under the ‘Material’ group will have all the available material information regarding the selected sections. In order to make sure you are looking at the complete list of material tables, check the ‘Show Advanced Data Classification’ option.
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The recent LTPP data analysis project conducted backcalculation of pavement structural parameters based on all of the falling weight deflectometer (FWD) deflection data collected until 2012. These backcalculated data can be accessed through the Data Selection and Download, SQL Export, and Table Export features.
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Please note that some of these data may be absent because some States or Provinces did not provide complete records of maintenance and rehabilitation histories. Any available information can be found under Maintenance and Rehabilitation (M&R) in the “Pavement Structure and Construction” class in the “Data Selection and Download” feature. In order to make sure you are looking at the complete list of tables, check the “Show Advanced Data Classification” option.
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The LAB_CODE field is a four-digit character field to help users identify where the laboratory is located and who performed the test. Using the STATE_CODE definition, the first two characters represent the State in which the laboratory is located. The third character indicates what laboratory performed the test (a coded value with details in the CODES table) and the fourth character represents the sample’s test number and is sequentially numbered from 1-9, then A-Z.
Climate
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The "Climate" class of the "Data Selection and Download" feature lists all the climate tables/fields that have available climatic information. In order to make sure you are looking at the complete list of climate tables, check the "Show Advanced Data Classification" option. You may also choose to narrow down your sections using "Find Sections" before selecting the data to get your desired data set.
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While LTPP has no official definition of climate regions for analysis purposes, LTPP InfoPave uses four climatic regions as ‘Wet, Freeze,’ ‘Wet, No-Freeze,’ ‘Dry, Freeze,’ and ‘Dry, No-Freeze’ to classify LTPP sections. The wet/dry regions are defined in terms of average annual precipitation (508 mm/year, 20 inches/year) and freeze/no-freeze regions as a function of average annual freezing index (FI) (83.3 degree-Celsius days). The average annual precipitation and average annual freezing index for each test section are computed using all data from 1980 until the latest available year of data in NASA’s Modern-Era Retrospective Analysis for Research and Applications, Version 2 (MERRA-2) dataset.
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MERRA-2 data is derived from a model with cells approximately 34 miles by 34.5 miles. MERRA-2 data starts in 1980.
VWS data is derived from ground measurements weighted by the inverse square of the distance from the LTPP section to measurement location. Results include three to fifteen measurement locations between one-quarter and fifty miles of the LTPP section within plus or minus one thousand feet of elevation.
Traffic
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The "Traffic" class of the "Data Selection and Download" feature lists all the traffic tables that have traffic information. In order to make sure you are looking at the complete list of traffic tables, check the "Show Advanced Data Classification" option. You may also choose to narrow down your sections using "Find Sections" before selecting the data to get your desired data set.
Performance
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The Section Summary Reports feature under Data is the best way to review performance data of an LTPP section. Under the "Graphs" tab of this summary report, you will see graphs of the major pavement performance information as a function of time. If you are interested in downloading the numerical data, you can use the “Go To” feature to go to the "Data Selection and Download" feature under Data and select the respective tables under "Performance." In order to make sure you are looking at the complete list of performance tables, check the "Show Advanced Data Classification" option.
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Once the sections are selected with “Find Sections”, open “Performance” and expand the JPCP tables under the Pavement Distress class to see the manual distress and faulting tables. To see other tables, click on "Show Advanced Data Classification.
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Diurnal collection of longitudinal profile using LTPP Directive P-58 during the minimum, maximum and mid-day temperatures was done for SPS-2, GPS-3 and SPS-8 rigid pavements. Similar data collection was done as a part of the Seasonal Monitoring Program (SMP). The sections for which this data exists may be selected using the “Diurnal Profile Data” filter under the Special Studies category of Find Sections. If the data is selected without using the filter, the VISIT_NO field should contain an “M” as the next to last character.
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Use the “Data Selection and Download” feature and expand the “Performance” class. The Backcalculation and Deflection class has the Deflection Data tables.
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Using the “Data Selection and Download” feature under Data, under the "Performance" class, check the “Show Advanced Data Classification” option. The Friction table will be under Surface Characteristics. If you click on “Add to Selection” option, you will be able to preview the data or you can select “Add to Data Bucket” option to download the data.
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