Travel Time Reliability Reference Manual/NPMRDS and INRIX Data Comparison
Comparison of INRIX and NPMRDS Data Sets
A comparison of speed data between INRIX and NPMRDS for January 2012 on a 4-lane inter-regional and 6-lane urban freeway.
| Urban 6-lane Freeway | INRIX | NPMRDS |
|---|---|---|
| Mean Speed (mph) | 61.05 | 56.90 |
| Standard Deviation (mph) | 4.61 | 6.24 |
| Median Speed (mph) | 61.72 | 58.05 |
| IR 4-lane Freeway | INRIX | NPMRDS |
|---|---|---|
| Mean Speed (mph) | 65.32 | 63.42 |
| Standard Deviation (mph) | 3.69 | 4.83 |
| Median Speed (mph) | 65.49 | 64.00 |
Particularly on the urban freeway, the NPMRDS data reports lower speeds than INRIX with higher variability. The matched pair graphs below reveal a similar trend represented by the linear fit with the intercept set to zero.
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