1. HPMS Sampling Issues Highway Information Seminar October, 2012

2. Selecting Samples Each individual urbanized area must be sampled independently States only sample their portion of a multi- State urbanized area 5-10% sample surplus per Volume Group is recommended

3. Why is sample management necessary? Road systems change over time Traffic volumes change over time Result: –Samples move among volume group strata –Impacts number of samples needed in each strata –Active sample management needed to maintain statistically valid sample

4. Reasons for Sample Panel Adjustments Boundary changes per the decennial Census The addition of small urban/urbanized areas Changes in functional system length due to reclassification or addition of roads

5. What can happen to samples? The sample may become biased The sample segments may be too short/long The sample may become non-representative –Rural/urban boundary changes, etc. Samples migrate among volume groups –Thus need to examine at volume group level

6. How to manage the sample? Perform regular sample reviews Plot the samples on a State map –Check for clustering on the same facilities, within an area, by volume group Review sampling procedures for bias

7. How to manage the sample? (cont’d) Run the HPMS 8.0 Software Adequacy Reports –check for unsampled volume groups –check for oversampled volume groups –check for undersampled volume groups –ensure a minimum 3 samples –maximum expansion factor of 100.000 otherwise too sparse for adequate representation

8. Adjusting the Sample Add/delete samples as needed –ensure all eligible segments are in the volume group for selection –use random process to select/delete samples FHWA would like to see sample deletion plan (for significant deletions) Adjust sample in timely manner prior to the next submittal cycle

9. Sample Maintenance Identify excessively short or long samples Lengthen short sections where possible Sub-divide long sections using software- generated TOPS sections

10. Useful Resources HPMS 8.0 Software 2010+ HPMS Field Manual Contact: Robert Rozycki– FHWA HQ Email: robert.rozycki@dot.gov, Ph: (202) 366-5059robert.rozycki@dot.gov