Travel Time Reliability Reference Manual/NPMRDS and INRIX Data Comparison

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Comparison of INRIX and NPMRDS Data Sets[edit]

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.

INRIX and NPMRDS Data Comparison on 4-lane Inter-regional Freeway in January Comparison between INRIX and NPMRDS Data on 6-lane Urban Freeway

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