Room to maneuver is always good. I always leave a couple car lengths between me and the vehicle in front both while driving and stopped. Its often an invitation to other drivers to fill that space but then I just start over. In motion it allows additional space and time to react in the event of a sudden maneuver by the driver ahead of you. At a stop it allows for additional space in the event of a rear end collision as well as the maneuvering space already mentioned.
Its also a good idea to be aware of any limitations due to the lane of traffic you may be in. Oncoming traffic, sidewalks (or lack thereof), pedestrian traffic, protesting crowds, etc may inhibit your ability to maneuver if you are trapped in the wrong lane.
I'd much prefer to observe, avoid, maneuver, and escape then to fight in or around my vehicle potentially against multiple agressors and with family in the car.
Fight would be one of my last options.