If you ride with a skittish horse the skittish horse rides nearer to the traffic. This stops the skittish horse shying at a leaf on the side of the road and pushing Steady Eddie into the traffic.
we had a horse inadvertently dump its rider then the mare trotted home, to get here she had to trot down a few miles of side streets and cross a six lane highway… the police car that was following her made no attempt to stop the mare as they said afterall she was stopping at all crossroads and looking both ways before stepping onto the road…even at the six lane highway she went to the median then stopped looked again the crossed when clear …then trotted to home sort of like the milk wagon horse of old days knowing the route
I used to have to ride a couple of stretches of pretty busy road to get to the trails (fortunately I don’t have to any longer). But I think the main thing is that YOU have to pay attention. Don’t be chatting away or staring at the landscape or wear anything that would obstruct your view or hearing. Being proactive and knowing a car is coming towards you makes all the difference in the world