To all others who are looking for these files:
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Sceneryobjects\Fellowsfilm Objects\Signs\Normal Road Signs\30 - Drive Carefully.sco
Sceneryobjects\Fellowsfilm Objects\Signs\Normal Road Signs\Street Sign 1 White.sco
Splines\whistlehead roadways\- Other splines\Roundabout.sli
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[1]The first two files can be found in the map of Scunthorpe, which is available at
FellowsFilm: Scunthorpe.
[2]The third one is tricky. This file is located in
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Splines\UKDT\Cotterell\whistlehead roadways\- Other splines
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of any version of
Cotterell map. So you need to create several folder series of "Splines\whistlehead roadways\- Other splines\" and then put all files relevant to Roundabout.sli to this new location.
[Conclusion]If you downloaded all the dependencies mentioned in the home page of this map or its readme file, plus two more steps mentioned above, your map of Yorkshire Counties should work well.