There are several instances where Compass data is not suited.
Absolute Volume
Connected Vehicle data represents only a portion of the traffic on our roads. The composition of cars across cities, countries and populations vary and so there is not a consistent composition and size. For example, a rural area is less likely to have as much traffic as inner suburbia and areas with a greater proportion of newer cars.
The data that is provided by third-party data aggregators is a sample. Not one vendor has access to all makes and models, as this is dependent on the variety of OEMs their data is extracted from.
To Replace Profilometer Data
While gyroscopic data from Connected Vehicles can be used to inform of changes in a road surface, it should not be used as a replacement for profilometer surveys.
Comparing Different Speed Methodologies and Expecting Similar Outputs
It’s important to be informed about what calculation methods are used in different contexts and collection methods to make informed and accurate decisions, particularly when comparing different data sources. For example, not all methodologies of calculating speed are the same or are applicable for all use cases.
Connected Vehicle data should not be compared to different methods of collecting speed data (tube counts, gantries etc) unless you understand the underlying methodology that is used to calculate those speeds. Because Connected Vehicle data is point data, it can be used as an input in several different calculations. Users need to ensure they are comparing the same methodology, not two different ones and expecting the same result (i.e., comparing vehicle harmonic mean speed with static point tube count data and expecting both methodologies to yield similar outputs). Read more about applying Connected Vehicle speed data in different methodologies here.