[Bug] Ways that do not match the era is built in some case

[Ranran(retired)]

New maps may inherit the default ways of previous saves and build ways that don't match the era.

Reproduction procedure:

(1) Start a new map in 2000.
(2) Build "ConcreteSteelCantileverRoad"
(3) Start a new map in 1750. (Don't end the game)
(4) Build "MasonryViaductRoad"
(5) You became a time traveler and brought asphalt roads to the 18th century. 

[Spenk009]

Is this due to the default selection of a waytype not resetting until manually done so? I've encountered the same issue, but being able to build track this way.