Gill,
In 1906 the roads in Ireland did not have official names. Dungiven road could have been the main road from Londonderry to Belfast via Dungiven or if one lived in Limavady it would have been the road from Limavady to Dungiven, now called Ballyquin Road. However if one lived in Dungiven the former road would have been the Derry road and the latter the Limavady road. Confusing!! Hopefully, from the information you have supplied, someone will be able to narrow it down.
Regards