Future research must show the validity of the theory on other roads in other countries around the world. Second, it is not clear how the data was interpolated. Kerner uses fixed point measurements (loop detectors), but draws his conclusions on vehicle trajectories, which span the whole length of the road under investigation. These trajectories can only be measured directly if floating car data is used, but as said, only loop detector measurements are used. How the data in between was gathered or interpolated, is not clear. The above criticism has been responded to in a recent study of data measured in the US and the United Kingdom, which confirms conclusions made based on measurements on the Bundesautobahn 5 in Germany. Moreover, there is a recent validation of the theory based on floating car data. In this article one can also find methods for spatial-temporal interpolations of data measured at road detectors (see article’s appendixes). Other criticisms have been made, such as that the notion of phases has not been well defined and that so-called two-phase models also succeed in simulating the essential features described by Kerner. This criticism has been responded to in a review as follows. The most important feature of Kerner’s theory is the explanation of the empirical nucleation nature of traffic breakdown at a road bottleneck by the F → S transition. The empirical nucleation nature of traffic breakdown "cannot" be explained with earlier traffic flow theories including two-phase traffic flow models studied in. The explanation of traffic breakdown at a highway bottleneck by a F → S transition in a metastable free flow at the bottleneck is the basic assumption of Kerner’s three-phase theory. However, "none" of earlier traffic-flow theories incorporates a F→S transition in a metastable free flow at the bottleneck. Therefore, none of the classical traffic flow theories is consistent with the empirical nucleation nature of real traffic breakdown at a highway bottleneck. The F→S phase transition in metastable free flow at highway bottleneck does explain the empirical evidence of the induced transition from free flow to synchronized flow together with the flow-rate dependence of the breakdown probability. In accordance with the classical book by Kuhn, this shows "the incommensurability" of three-phase theory and the classical traffic-flow theories (for more details, see):  The minimum highway capacity formula_16, at which the F→S phase transition can still be induced at a highway bottleneck as stated in Kerner’s theory, has "no" sense for other traffic flow theories and models.