Reduce speed limit

Our rural road has a national speed limit along it, which we believe needs reducing down to 40mph.
We lead and ride horses along this road to get to our turnout paddocks and have no other option but to use this road.
Drivers come far to fast around corners not expecting us to be on the road and there has been a lot of moments that have been very close to nasty accidents. I really hope this speed limit can be reduced before a horse/person gets seriously injured or killed.