Updated: FHWA published the final rule on January 18, 2017. Although it streamlined and improved some things – including several of the recommendations coming from UW-Madison and GLRTOC (see comments document below) – it introduces greater reliance on HPMS and volume data, which entails greater complexity. See the FHWA page for more information.
The one metric/measure than can be calculated from NPMRDS travel time data alone is for freight reliability performance.
The following table summarizes the results of the Freight Reliability Measure for our ten member states for 2015 and 2016. As detailed in the final rule, this is the distance-weighted average of the maximum TTTRs.
State by state tabular reports of all segments and various values required for reporting are available by request.
“On April 22, 2016, FHWA published a Notice of Proposed Rulemaking (NPRM) in the Federal Register to propose national performance management measure regulations to assess the performance of the National Highway System, Freight Movement on the Interstate System, and the Congestion Mitigation and Air Quality Improvement Program, as required by the Moving Ahead for Progress in the 21st Century Act (MAP-21) and the Fixing America’s Surface Transportation Act (“FAST Act”).”
As published in the Federal Register the NPRM is 109 pages of dense information. That will not be repeated or synthesized here because there exists of wealth of information via the official FHWA page for this, including fact sheets, webinar recordings, the NPRM itself, and related resources.
Through a current MCOM project, GLRTOC has been generating mobility performance measures for member agencies for several months, primarily utilizing the NPMRDS. Because the NPMRDS is the key proposed data source in the NPRM, we are able to provide technical comments, analysis, and preliminary results here.
Slide sets are available summarizing the measures, inputs, process, and comments.
- June 2016 Midwestern/GreatLakes ITE Conference and SimCapUsers Group (PDF 5.6 MB)
- May 2016 Discussion and Comments (PDF 3.3 MB)
Results as Proposed
While the comments and results shown below and in the comments document include recommended variances from the NPRM, we have produced results for Iowa, Kansas, and Wisconsin for Subparts E and F statewide interstates exactly as proposed in the NPRM. The Wisconsin results are included in the comments document linked above.
- Iowa – view or download the Iowa results and observations here (PDF)
- Kansas – view or download the Kansas results and observations here (PDF)
Please send feedback, questions, and requests to firstname.lastname@example.org.
NPRM Measures Summary
|E||Level of Travel Time Reliability (LOTTR)||% of Mileage Reliable (80th/50th < 1.5)||Statewide||Interstate and Other NHS||3 Weekday and 2 Weekend Blocks||Include||Do Nothing||Fill in with TT@PSL|
|E||Peak Hour Travel Time Ratio (PHTTR)||% of Mileage Meeting Expectations||Metro 1M+||Interstate and Other NHS||Weekday Peak Hours||Exclude||Remove Outside 2-100 MPH||Do Nothing|
|F||Truck Travel Time Reliability||% of Mileage Reliable (95th/50th < 1.5)||Statewide||Interstate||All||Include||Do Nothing||Slower of All Veh or TT@PSL|
|F||Average Truck Speed||% of Mileage Uncongested ( > 50 MPH)||Statewide||Interstate||All||Include||Do Nothing||Slower of Al Veh or TT@PSL|
|G||Total Excessive Delay||Hours of Delay per Capita||Metro 1M+ Nonattain. or Maint.||All NHS||All||Include||5-minute Delay Ceiling||Do Nothing|
|H||Project Emission Reduction||Total Emission Reduction||Metro 1M+ Nonattain. or Maint.||N/A||N/A||N/A||N/A||N/A|
For example, depicted per TMC are the two reliability ratio metrics, the maximum average peak hour speed (an input into the PHTTR metric), the average truck speed, and the time-based delay (which when combined with volumes becomes the delay metric).
Travel Time Reliability (Subpart E)
This is a statewide measure of the percent of mileage providing for reliable travel. A segment is reliable if the ratio of 80th to 50th percentile travel time is less than 1.5 in all of four blocks of time during the week. The measure calculated for interstates and for non-interstate NHS separately.
A key sticking point (as proposed) is the need for accurate posted speed limit data for each of the ~300k NPMRDS segments across the entire NHS. This does not exist. The comments document linked above details this issue and encourages better alternatives.
Here are two bar charts illustrating preliminary results of the Subpart E measures in 2014 and 2015 for all ten Mid-America states. First is interstates.
Peak Hour Travel Time (Subpart E, continued)
This measure applies only to the most populous urbanized areas, which for the GLRTOC members includes Chicago, Detroit, Minneapolis-St. Paul, St. Louis, Cleveland, Cincinnati, Kansas City, Indianapolis, Columbus, and Milwaukee. The measure is the percent of mileage, again for interstate and non-interstate NHS separately, where peak hour travel meets “expectations.” It is straightforward to calculate the maximum average peak hour travel time as proposed, which we have done and will be displaying in an online map here shortly, but “expectations” or “desired” travel times must be agreed upon between State DOTs and MPOs.
To provide an illustration for now, assume a blanket “desired” speed of 20 MPH. The PHTTR metric is the ratio of the maximum average peak hour travel time to the “desired” travel time. If a segment exceeds 1.5, or less than 30 MPH in this illustration, it gets counted against the measure. The following plot shows what the percentage of interstate mileage would be in 2015 for the ten largest metros.
Reliable Truck Travel Times (Subpart F)
This is conceptually similar to Travel Time Reliability above, but a) it uses freight travel times where available, b) all times of the year are used instead of certain blocks, c) the numerator is the 95th percentile instead of 80th, and d) it only applies to interstates statewide.
This also only applies to interstates statewide. For this measure, a segment is considered “uncongested” if the average freight speed is faster than 50 MPH.
This is a measure of vehicle delay reported per capita. It applies to all NHS in the largest metro areas that are in CMAQ nonattainment or maintenance. Calculating this entails volume data collection and conflation, making it more technically difficult than the others (i.e., sorry we don’t have results to show just yet). Functional classification data per segment is also needed, as that determines the baseline speed for delay.
On-Road Mobile Source Emissions (Subpart H)
This is very different from the others and is not addressed by GLRTOC. It applies to CMAQ nonattainment or maintenance areas, and the data source is only the CMAQ Public Access System.