I got this error when loading a save file for the first time with Asphalt Roads 1.1.5:

85.360 Applying migration: Asphalt Roads: asphalt_roads_1.1.0.lua
85.599 Error AppManagerStates.cpp:1397: Error while applying migration: Asphalt Roads: asphalt_roads_1.1.0.lua

AsphaltRoads/migrations/asphalt_roads_1.1.0.lua:6: attempt to index field 'Arci-marking-yellow-dl-straight' (a nil value)
stack traceback:
AsphaltRoads/migrations/asphalt_roads_1.1.0.lua:6: in main chunk

Steps to reproduce:
Start a game without any mods installed. Save the map.
Install Asphalt Roads. Disable single and double yellow road line markings in startup settings. Restart Factorio and load the save.

Strangely, I did not get an error the first time I added it to my server's map, but now with Factorio 0.17.31 I can reproduce this crash as described above.

Thank you for your report, i think i know where the problem is. The migration file was written before the option to disable some of the lines was added and is therefore missing some safety checks regarding disabled tiles. Strangely, i did not experience the issues you described before.
I'll fix this in the next two days.

The fix is ready, please see the latest version.