Summarize this article in one sentence.
If you're traveling alone, you're often an easier target than with a group of friends or relatives.  Groups of teens often are more inclined to act out when in a group.  Their group is their security, and they may want to show-off in front of their peers.  Find ways to travel more often with someone you trust, particularly at night or in areas where you know there's been trouble. While this may not come easily, it's important to see that increasing your self-esteem will allow you to act and behavior more assertively.  Try to dress and do things that don't draw attention to yourself in a way that may lead to ridicule.  Bullies often find ways to make others feel more vulnerable, so blending in may be helpful. By participating in a class, the act of taking action will lead to greater self-esteem, and in turn a greater sense of strength.  Most martial artists will tell you that the first day you start a martial arts class is ironically the last time you ever fight. With the use of discipline as taught in martial arts, the ability to walk on past a group of bullying teens will seem much less intimidating. If there's a group of teens who aren't actively provoking you, but just acting a little suspicious, try breaking the ice.  Consider having a brief but positive conversation with them, rather than assuming it will be negative.  Sometimes loitering teens just want to have a purpose, particularly if they're hanging out in the same spot regularly.  Consider engaging them in a useful way, like being a look-out for other suspicious activity. Or just simply introduce yourself and make small talk. See if being "neighborly" reduces the negativity.

Summary:
Travel in groups of two or more. Dress and act with confidence. Learn self-defense such as martial arts, or take a self-defense class. Try having a positive interaction with them.