Here's a link to the best online introduction to Freudian dream analysis that I have seen. If you really want to get into it, a beautiful new version of Freud's Intrepretation of Dreams is available. From the site:
"I had a dream in which I was at a party with my sister and a friend. My sister had sex with a guy right next to me while I was passed out asleep because I was drunk. I slept for a few hours and then woke up and went back to the party. There was a guy there who had two visor hats over his face and everybody was afraid of him. We then started driving and racing. Everybody pulled over for him to pass them, except for me. He was really mad that I wouldn’t pull over and was getting violent. He tried to crash into me, but I pulled ahead and got away. Then there was an accident behind me with two other cars."
Perhaps I am feeling resentment for a family member or friend and view them as having more than me, as I am currently not in a relationship and not having sexual relations. Maybe the scary man represents men in general and me being intimidated by them and not being able to trust in order to date. If I did date someone at this time, it might be a mistake, causing an "accident."
Freud might say:
The dreamer is asserting strength and independence against problems known (sister issues, which may be in a completely different form than in the dream) and unknown (the visored male driver). The latent associations for the visor and threatening drivers should be explored. This may be the desire of the female to have control over the masculine influence in her life, or a generally threatening influence.
I would add: Let's not forget that Freud thought that all dreams were disguised wish fulfillments. What are this dreamer's latent wishes, as symbolically revealed in the dream? Voyeurism, perhaps, in her sister having sex right next to her. But if the sister is actually a displaced version of herself, then the wish could be to take the passive role in sex, to not have to initiate sex but to simply receive it, while completing giving in to her desires ("passing out").
The two-visored man is interesting, but I agree that it is up to the dreamer to figure out who or what he represents. If she means a man with a motorcycle helmet with two visors, then I would suggest that wearing a motorcycle helmet would add a bulbous quality that might make him look like a walking penis, and hence a pretty obvious phallic symbol.
Racing dangerously suggests the unconscious desire to give in to one's instincts. "To crash into me" seems like a pretty clear sexual penetration symbol in this female dreamer. Perhaps the wish is to lead a man on to the point of his losing complete control of himself, to cause a man to become so sexually desirous of her that he destroys himself (and whomever else he was near). Freud would call that sexual sadism.
Freud never said that you would like what you find out about yourself in your dreams. There's a reason that the material is disguised and distorted, and a reason why you have dreams about these dark impulses rather than act them out during the day.