You can try a dream journal, as said above, for help with dream recall. But another idea is you could try to learn to WILD. Don't be thinking about the dream while you try to WILD, which might take a day to years to get right. WILD guides can be found all over Dreamviews, such as here. If you end up getting good at WILDing, you can try talking to your subconscious. Talking to dream characters, which are projections of your subconscious, or going onto a computer database or file cabinet (some sort of mass storage device in your dream), can sometimes extract information.
If you don't want to or can't ask your subconscious for answers, you can try to find out for yourself. Once you have experience with WILDing you'll have better control over all of your dreams. And one night you can be in a WILD, concentrate on changing your surroundings, and enter your old nightmare. Perhaps try viewing it like on a television, be a bystander, or be in your dream as usual (but being careful of losing control). Then maybe instead of crossing the road, you can do something else, and see how the dream reacts.
Keep in mind that mastering WILDing isn't instantaneous, but might give you the most satisfying and useful results.
Good luck.