> Plus, you have no idea what time of day the car will be passing through a location.
I don't, but I assume google does.
> So you can't compare the data points over time - they're not taken the same time of day
Not in a simple way, no. But to say it doesn't provide useful information seems odd when the article says
> Independent scientific analysis confirmed that the mobile sensor system worked for collecting street-by-street data, and could improve upon the regional network of sensors operated by the Environmental Protection Agency.