Human-centric: The background of the OTU features a human-dominated universe. As such, the core rules primarily focus on development of human characters touching only briefly on a few non-human species. There are numerous Traveller publications however, with rules and extensive information on playing members of other races.
Cosmopolitan: Despite the dominance of humanity, a large number of aliens was always implied to exist, inside and outside of Charted Space. The number of aliens per sector is estimated to vary from zero (in “barren” sectors) to eight or more (for example, in the Spinward Marches sector).
Interstellar travel: Interstellar travel is facilitated, and limited, by the use of a technology called the jump drive. These drives are capable of propelling a spacecraft between one to six parsecs depending on the individual drive’s specifications. Regardless of the distance of a jump, the duration required for the trip is approximately one week, thereby recreating an “age of sail” feel to the game.
Limited communication: A central theme to Traveller is that there is no form of faster-than-light information transfer – meaning no ansible, subspace radio or hyper-wave communication technology is available. Most interplanetary communication is handled by courier ships, most commonly “X-boats”, which are small Imperial vessels with long-distance jump drives that travel between systems transmitting and receiving vital data. Systems not on an X-boat route must rely on mail runs brought in by visiting ships.
The new feudalism: The restraint on the speed of information leads to decentralization and the vestment of significant power in the hands of local officials. This isolation causes entire wars to be fought, won, or lost on the frontiers before a message gets to any remote administrative capitals to let them know the war has even begun. This means that all kinds of agents, from merchants to generals, must show initiative and be reasonably independent from their corporate or political overlords. Since local rulers cannot be directly controlled by central authority, affairs are managed by a class of independent nobility, who make use of classic titles such as Baron, Duke and Archduke. This decentralization of authority is one means of coping with the difficulties imposed by size and limits of speed of transportation technology.
Non-utopian future: In the OTU, the human race never evolves into a superior state. People remain people and continue to show courage, wisdom, honesty and justice, along with cowards, liars, and criminals. Tension is vented regularly in small conflicts before they have a chance to reach Imperium-shattering proportions. Thus, planets are allowed to fight out internal wars, and capitalism is the major driving force of civilization.
No prime directive: There is typically no prohibition on contact or interference with other races protecting them from advanced technology. Economics and other factors that applied to exploration and colonization on Earth are the same factors that shape the Traveller Universe. However, governments may interdict planets with native primitive intelligent species. These interdicted worlds are commonly known as “Red Zones” based on the Imperial designation for such a world. ‘Red’ (or the less restrictive ‘Amber’) zones are often to protect the interest of an interstellar government, not the native population.