High-quality data are critical for validly monitoring progress toward global initiatives related to road traffic crash prevention. We assessed the availability and consistency of road traffic mortality data from health and non-health departments in national governments, plus changes in data consistency over time from 1985 to 2013. Using freely accessible data, we systematically assessed availability and consistency of health and non-health data from 1985 to 2013 in 195 countries. Data availability was reflected by the presence of data on motor vehicle mortality rates in that country at any points between 1985 and 2013. The ratio of ‘health data divided by non-health data’ was calculated to measure the consistency of the two types of data sources. We found that 77 of the 195 countries in the world (39%) had both health and non-health data sources available from 1985 to 2013. None of the 34 low-income countries had both kinds of data sources simultaneously available, while 41 of 55 high-income countries had both kinds of data sources. Of the 71 countries having both kinds of data for five years or more, 33 countries demonstrated high consistency between data sources, 25 countries showed moderate data consistency, and 13 countries displayed low consistency. Jamaica, Mexico, and China had the largest data inconsistencies. 26 of the 71 countries witnessed improved data consistency between 1985 and 2013, but nine experienced decreasing data consistency, in a few cases to a large degree. Efforts are needed to identify reasons leading to data quality changes, and to develop approaches to improve data quality in those nations where it is inadequate.