The difficulty with eye contact is that it's easy to interpret as being there when the other person really just looks through you. Very common to hear about accidents when one person was confident they had eye contact and then the other just had no idea they were there.

In fact, eye contact works so badly for me that I prefer looking at the front tyres – their direction and angular acceleration tells me a lot more about where the vehicle is about to be.

Pointing, however, is very explicit and rarely happens by accident.