Cellular Automata rules lexicon 

Family: Special rules 
Type: depends to the rule
"Special rules" game contains nonstandard rules that cannot fit into any other game and cannot be programmed as external DLLs due to violation of syntax or MCell principles. Currently only one rule exists here  "Traffic CA" by David Griffeath and Larry Gray. It's a probabilistic onedimensional rule that cannot be programmed as an external DLL because it can modify 2 cells when certain neighbourhood conditions are met.
The syntax of each "Special rule" can be different.
Traffic moves to the right, so the only possible transitions are of the form 10 to 01 at some pair of adjacent sites. Four paramaters – a, b, c, and d – govern such transitions, synchronously in time. The advance probabilities are:
The text notation of Traffic CA rule has the "TRCA,a,b,c,d,p1,p2" form, where:
TRCA  fixed prefix,
a,b,c,d  acceleration, braking, congested, driving; values in a range <0..1>,
p1, p2  probability of placing new cars on left and right side; values in a range <0..1>.
Name  Rule  Character  Description 
Traffic CA Standard  TRCA,0.11,0.05,0.1,0.1, 0.2,0.2  Stable  Probabilistic Traffic CA by David Griffeath and Larry Gray. This CA allows exploring mechanisms for the onset of traffic jams due to acceleration and deceleration of cars within a homogeneous singleline stream. 
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Last update: 15 Sep 2001