Generally, referring to somebody as a 'slug' isn't likely to be a good way to make new friends. In Virginia, though, being a slug might just be a great way to meet new people while saving some cash. How so? Apparently, 'slugging' refers to catching rides
with people you don't know. The goal, of course, is to cut down on fuel consumption and travel time by using the carpool lanes. Drivers and riders meet up at specific parking lots early in the morning and discuss where everybody is headed. Once a slug finds a driver who is going to same place that they are, the trip is on.
It seems that the practice of slugging began in Virginia over thirty years ago. According to Virginia Department of Transportation estimates, 6,500 commuters a day slug or pick up slugs. Authorities in Virginia have nothing to do with the practice and say that the lines form all by themselves. Slugging works near the Nation's Capitol because most jobs are concentrated in a small area and most people live outside the actual city. What's more, many slugs are government workers, and there is a sense of trust between them.
[Source: Hampton Roads