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National Performance Management Research Data Set (NPMRDS)
Technical Frequently Asked Questions

December 2013

This document serves as a guide to answer frequently asked questions regarding the National Performance Management Research Data Set.

Data Download Questions

  1. Would it be possible to get surrounding state data for use in calibrating our statewide model?
  2. Are there instructions on how to obtain the data?
  3. It would be helpful to have the data sets downloadable by metropolitan planning area. Is that possible?

Shapefile Questions

  1. Are incidents included in the data such that we can know why the spikes?

General Data Questions

  1. What time zone are the epochs reported in? Is it the local time for each TMC segment?
  2. What is the meaning of the T and F values in the Dir_Travel field?
  3. Is there any distinguishing transit travel data in the data set?
  4. What is the definition of a "reference node"?
  5. What are the data sources used to capture this data?
  6. If the static file changes, will the new file still usable with previous months?
  7. When combining truck and car data, how do you get volumes of each to weigh them proportionately?

Table Join Questions

  1. Will joining be a faster join if we index the data?
  2. Does this join process need to be done each month as the data is made available?

Data Download Questions

  1. Would it be possible to get surrounding state data for use in calibrating our statewide model?
    Yes. Agencies with access to the data may download other states' data too. The map below shows how the regions are divided across the United States. Additional road coverage beyond the NHS may be requested separately through HERE and is not a part of the NPMRDS.
    The map illustrates that the data set is divided into regions. There are four regions: Northeast Region, Southern Region, Middle Region, and Western Region.

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  1. Are there instructions on how to obtain the data?
    To request access to the data (if you are a state DOT or MPO), please send an e-mail to heretraffic.nhsdata@here.com. Once granted access, you will be sent instructions on how to access and download the data.

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  1. It would be helpful to have the data sets downloadable by metropolitan planning area. Is that possible?
    Data sets can be downloaded only by region and then state only. Further extraction can be done by "county" field in the static file.

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Shapefile Questions

  1. Are incidents included in the data such that we can know why the spikes?
    There is no incident data in the NPMRDS. These can be obtained separately through HERE if needed. Please contact: heretraffic.nhsdata@here.com.

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General Data Questions

  1. What time zone are the epochs reported in? Is it the local time for each TMC segment?
    All times are local.

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  1. What is the meaning of the T and F values in the Dir_Travel field?
    T is "Towards" reference node and F is "From" reference node. More details are available in the provided Shape file specification document.

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  1. Is there any distinguishing transit travel data in the data set?
    The data set only contains passenger and freight vehicle travel data for the road network. HERE provides Transit and Pedestrian data as a separate product offer.

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  1. What is the definition of a "reference node"?
    Reference node is synonymous with "start" or "from" node in Esri terminology. It represents the starting point of the linear segment in order to interpret the direction and left and right sides of the line (or in this cast the road). In the HERE map it is defined as the most southern and western most nodes on the LINK. See the shape file specification document for more detail information.

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  1. What are the data sources used to capture this data?
    • Passenger probe data is obtained from a number of sources including mobile phones, vehicles, and portable navigation devices
    • Freight probe data is obtained from the American Transportation Research Institute leveraging embedded fleet systems

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  1. If the static file changes, will the new file still usable with previous months?
    Yes, TMC information is backward compatible.

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  1. When combining truck and car data, how do you get volumes of each to weigh them proportionately?
    For the All Vehicles Travel Time, the observable data for both passenger and truck vehicles are used in the calculation. For example, if there are 10 observations for passenger and 2 for freight, the weight will be heavier for passenger.

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Table Join Questions

  1. Will joining be a faster join if we index the data?
    Yes, the join will be faster if you index the data.

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  1. Does this join process need to be done each month as the data is made available?
    Yes, but only the Travel Time data for that specific month needs to be re-joined. The other data sources used (static file, shape file) don’t change every month.

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Staff Contacts

Jeff Purdy
202-366-6993
Jeffrey.Purdy@dot.gov

Vince Mantero
202-366-2997
Vince.Mantero@dot.gov
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