Custom Roundabouts

[TheMightyJiggles]

I was wondering how i could create a custom roundabout. I have looked for a uk prefab without sidewalks but haven't found one. All the prefabs I have found are European prefabs. I have also tried editing the prefabs but it failed to recognise the prefab file. I am also familiar with blender but I would prefer just using the map editor to create the roundabout.

Any Help would be greatly appreciated.