Nope, because different roads of the same type can have different speeds in close proximity. And Roads of the different types can have the same speed settings.

Example a road called Hwy 89 that runs from Canada to Mexico through Montana, Idaho, Utah, and Arizona. The legal speed limit on this road changes constantly across it's length, in many areas it's a two lane rural highway with a speed limit of 55, but every time it enters a city the speed limit will drop, some times to 45 sometimes to 35 and even all the way down to 25. In other areas it's basically a freeway with a speed limit of 65 which of course means drivers cruise at 75 to 80. Yet across it's length except for when it merges with an actual Interstate freeway, it is Known as Hwy 89 and is marked as either a minor or a major highway. Most of it's length is classified as minor highway with a few higher volume segments as Major or even freeway (when merged with a freeway).

Your system would change a very consistently classified road into a hodgepodge mess of different classifications which would also trash the routing along the Hwy. Even though the speed limit changes frequently along this road, for most of it's length it is a primary travel route and should be preferred in the routing algorithms even though it's speed drops to 25 mph through some towns.