Jun Senoue on Sonic Generations Original Soundtrack:

Speed Highway

In White Space-Time, from this stage onward, we decided the modern versions to be near the originals and in the classic versions, we composed in such a way that they could let us feel more freshness and surprises. This modern version is the impression of faithfully updating the proportion and the original, but in the halfway inserted Skyscraper Downhill, we decided the remix with more effective edge and others. Actually, it is longer than the version used in the game, so even if the building that Sonic runs down became a higher skyscraper, it would be the impression that we could sufficiently make use of.

On the other hand, for the classic version, the game was felt as something that placed more emphasis in the mechanism than the original, so aiming at the remix full of gimmick feeling as well, Cash Cash completed the composition.