Request route/roads only change to asphalt when entering the modern era instead of the industrial era.

[arcvoodal]

I cannot for the life of me find anything in the xmls (such as EraInfo.xml) that allows me to change which era the textures of the roads become asphalt. I would like to change it so that the roads only change to asphalt when entering the modern era instead of the industrial era. Anyone know how to do that?