'movement difficulty' is incorrect when building into a biome with a different movement difficulty

[mvadovszki]

Example -
If you build a new asphalt road from 'Temperate Forest' (1) to 'Temperate Swamp' (4), (or vice versa)
The 'Temperate Forest' becomes .1 (should be .4), the 'Temperate Swamp' becomes 1.6 (should be .4)

If you extend an existing road on 'Temperate Forest' into 'Temperate Swamp' (4),
The 'Temperate Forest' will remain unchanged at .4, but 'Temperate Swamp' becomes 1.6

The issue seems related to the biome difficulty reduction,
it does not affect 'dirt path+' since this does not reduce biome difficulty,
it is preset in pre-generated roads.