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A Percentile Skill System for Traveller

Traveller rawks, there's no doubt about it. And you can get D6's pretty much anywhere. In fact at my parent's house, all the board games in the cupboard are pretty well diceless from constant raids over the years.

But I'm a big fan of % systems, especially the Chaosium system, which I regard as one of the more elegant and simple mechanic sets in gaming today, especially in regards to skill advancement. So if you like it as much as me then here's how you can adapt Traveller to a % system.

Step 1: Assign base values: In blocks of 5% go through whatever skill list you are using and assign a base skill % rating. This is the basic chance that someone attempting a task with no real knowledge in that skill has in succeeding. For example shooting a pistol is largely point and click (stuff about proper grip, flicking off the safety etc aside). Let's give Handguns a base value 20%. Physics is an ornery cuss that needs to be tamed by the mathematically inclined. Let's give it 0%. For your benefit I have included a table converting listing recommended values for Mega Traveller skills.

Step 2: Assign each skill a relevant stat grouping: Stat groupings are as follows

Agility - Used for physically-focussed skills such as Brawling or Blade combat.
Primary: Dex
Secondary: Str
Charm - Used for interpersonal skills like Liaison or Interrogation
Primary: Social (or Cha if you use that stat)
Secondary: Int
Knowledge - Used for intellectually-focussed skills like History or Physics
Primary: Educ
Secondary: Int
Manipulation - Used for fine-motor and coordination skills, such as Gun Combat, Electronics, or Mechanical
Primary: Dex
Secondary: Int

Each stat grouping has a primary stat and a secondary stat. Primary means a Traveller adds (Value of stat – average value)*2 to the % chance for that skill. Secondary means the Traveller adds (Value of stat – average value) to the % skill. Average value depends on which brand of Traveller you are adapting. Classic Traveller, MegaTraveller, and Marc Miller's Traveller (T4) had an average stat value of 7 (2D); Traveller: The New Era had an average stat value of 5 (2D-2).

For example, the ubiquitous Terry has a MegaTraveller UPP of 7A6864. The Average stat value is 7. Terry's modifiers would be as follows:

Agility: +6
[(Dex A(10)–7 = 3, multiplied by 2 for a result of 6 plus a Str mod of (STR 7-7= 0).]
Charm: -5
[(Social 4-7= -3, multiplied by 2 for a result of –6 plus an Int mod of (Int 8-7 = 1)]
Knowledge: +1
[(Int 8 –7 = 1, multiplied by 2 for a result of 2 plus a Educ mod of (Educ 6 -7 = -1)]
Manipulation: +7
[(Dex A –7 = 3, multiplied by 2 for a result of 6 plus an Int mod of (Int 8-7 = 1)]

Again, for your benefit, see the MegaTraveller conversion table at the end of the article.

Step 3: Convert current skill levels to % values and add to base skill chance.

This is the easy part. Simply add as follows

Skill Level  % Bonus
0 +10%
1 +20%
2 +40%
3 +60%
4 +70%
5 +80%
6 +90%

For each level beyond 6 add 5% (although few GMs would allow skills to get this high).

'Serves As' Skills: If a Traveller has a skill that 'serves as' other skills then treat each skill in the combination separately. For example, in MegaTraveller Liaison serves as Admin minus 1 and Streetwise minus 1. A PC with a skill of Liaison-3 would add 60% to their Liaison % value and 40% each to their Admin and Streetwise % values.

Example of conversion: Terry from the above example has a carousing level of 1. The GM (me in this case) decides this is an every man skill and gives it a base value of 20%. I assigned Charm as the appropriate skill grouping. Terry's modified chance looks like this

20% (Base) –5% (Charm modifier) + 20% (skill level 1) = 35%

Skill Resolution: It's a simple matter of if the % dice equal or are less than the Traveller's % chance then they succeed. This assumes a difficult task. For easier tasks modify the chance by blocks of 10% upward. For example, a Routine task might be +20, Simple might be +40%. For stupidly harder tasks, modify in blocks downward, e.g., a Formidable task might be –20.

Experience: This is the best part. The Traveller experience systems were always pretty harsh on the old PC. And let's face it, players love nothing more than advancing their PC's skills. While us mortals spend our leisure time watching TV, or gaming, our fictional counterparts are hitting the gym or the books, watching what they eat, and so forth.

Again, borrowed from Chaosium, experience is simple. If a Traveller succeeds at a skill during a game session than the GM feels advanced the story and so forth, they can check it. At the end of the session they roll % dice. If the result is equal or exceeds their current skill then increase the skill % value by roll D10/2. The beauty is that probability means that higher skill % chances will be much harder to obtain.

Training: Once a PC spends (current skill %) hours dedicated to training in a specific skill they can make an Intelligence roll. If they succeed they get a skill check. The GM is free to modify the roll for access to instructors, training aides, conditions or study etc.

Statistic % checks: Naturally if you've gone and applied the above, you'll want to do the same for stat checks.

For Classic and MegaTraveller, and T4 where the average stat value is 7, add 3 and multiply the result by 5. Eg 7+3 is 10. Multiplied by 5 is 50%. For New Era, where the average is 5, double the value then multiply by 5. Eg 6x2 is 12. 12 Multiplied by 2 is 60%.

Advancing Stats: If a Traveller checks a stat, make the experience roll as normal, adding any % boost to the stat % value. When their stat % value reaches a multiple of 5, increase the actual stat value by 1 point. Eg Terry has an Int of 8, with a % value of 55%. He manages to get 3% added to his Int % chance. So his stat reads Int 8 (58%). When it gets to 60%+ he can boost the actual value of 8 to 9.

Table 1; Mega Traveller converted to % skill system

Skill Base Skill % Skill Group
Administration 10 Charm
Artisan 10 Manipulation
Axe 10 Agility
Battle Dress 0 Manipulation
Biology 0 Know
Blowgun 5 Manipulation
Bola 0 Manipulation
Boomerang 0 Manipulation
Bow 10 Agility
Brawling 20 Agility
Bribery 10 Charm
Broker 10 Charm
Carousing 20 Charm
Chemistry 0 Know
Combat Engineering 0 Know
Combat Rifleman 10 Manipulation
Communications 10 Know
Computer 0; 20 if tech 9+ Know
Crossbow 10 Manipulation
Cudgel  20 Agility
Demolition 0 Manipulation
Disguise 5 Charm
Early Firearms 5 Manipulation
Electronics 5 Manipulation
Energy Weapons 5 Manipulation
Engineering 0 Know
Equestrian 10 Agility
Fleet Tactics 0 Know
Foil 10 Agility
Forensic 0 Know
Forgery 0 Manipulation
Forward Observer 0 Know
Fusion Gun 0 Manipulation
Gambling 10 Charm
Genetics 0 Know
Grav Belt 0; 5 if tech B+ Manipulation
Grav Vehicle 0; 20 if tech 9+ Manipulation
Gravitics 0 Know
Guard/Hunting Beasts 5 Charm
Handgun 20 Manipulation
Heavy Weapons 5 Manipulation
Helicopter 0 Manipulation
Herding 5 Charm
High Energy Weapons 0 Manipulation
High-G Environment 0 Agility
History 15 Know
Hovercraft 0 Manipulation
Hunting 5 Know
Instruction 10 Charm
Interrogation 5 Charm
Interview 10 Charm
Intrusion 0 Manipulation
Jack-of-all-trades See note 1
Jet-propelled Aircraft 0 Manipulation
Large Blade 10 Agility
Large Watercraft 5 Know
Laser Weapons 5; 20 if tech 9+ Manipulation
Leader 15 Charm
Legal 5 Know
Liaison 10 Charm
Lighter-than-air Craft 0 Manipulation
Linguistics (see note 2) 5 Know
Mass Driver 0 Manipulation
Mechanical 10 Manipulation
Medical 5 Know
Meson Guns 0 Manipulation
Mortars and Howitzers 0 Manipulation
Naval Architect 0 Know
Navigation 0 Know
Persuasion 10 Charm
Physics 0 Know
Pilot 0 Manipulation
Plasma Gun 0 Manipulation
Polearm 5 Agility
Propeller-driven Aircraft 0 Manipulation
Prospecting 0 Know
Reconnaissance 10 Know
Recruiting 5 Charm
Rifleman 20 Manipulation
Robot Operations 0; 10 if tech A+ Know
Robotics 0 Know
Screens 0 Manipulation
Sensor Operations 0 Know
Ship Tactics 0 Know
Ship's Boat 0 Manipulation
Sling 0 Manipulation
Small Blade 15 Agility
Small Watercraft 0; 5 if hydro 4+ Manipulation
Spinal Weapons 0 Manipulation
Stealth 15 Agility
Steward 20 Charm
Streetwise 5 Charm
Submachinegun 10 Manipulation
Survey 0 Know
Survival 0; 10 if atmos 4-9 Know
Tactics 5 Know
Tracked Vehicle 5 Manipulation
Trader 5 Charm
Turret Weapons 5 Manipulation
Vacc Suit 0 Agility
Wheeled Vehicle 0; 10 if tech 4-8 Manipulation
Zero-G Environment 10 Agility
  1. J-O-T is harder to convert. I recommend the following. Each session the Traveller is allowed (J-O-T level) automatic re-tries at a failed skill roll without having to make a determination check.

  2. For each level of Linguistics the Traveller receives their Educ % stat value in a specific language, e.g.,Terry has Linguistics-2 and can speak Vilani and Gvegh. His Educ % value is 45%. He gets 45% in Vilani and 45% in Gvegh. From this point he advances in those languages normally. Once converted Linguistics no longer offers automatic language ability. Instead if a Traveller's Lintuistics skill % is higher than a language %, they double any skill advancement rolls.