разгруппируй переменные на большее количество групп.
основные переменные, т. е. те из которых можно вычислить остальные;
дублирующиеся переменные;
и так далее... 

-- Vehicle Controls

local horn                  -- 0 or 1     - Indicates the horn is active.
local parkingbrake          -- 0 to 1     - Parking brake input
local parkingbrake_input    -- 0 to 1     - Parking brake input
local reverse_gear          -- 0 or 1     - Indicates a reverse gear is selected.
local steering              -- Degrees    - Angle of the steering wheel.
local steering_input        -- 1 to 1     - Steering input percentage.
local throttle_input        -- 0 to 1     - Throttle input percentage.

-- Lights

local brakelight_signal_R   -- 0 or 1     - Combines the brake electrics with the signal_R electric. Lights up if either of those are on. Used for american style indicator/lights.
local brakelight_signal_L   -- 0 or 1     - Combines the brake electrics with the signal_L electric. Lights up if either of those are on. Used for american style indicator/lights.
local fog                   -- 0 or 1     - Indicates the foglights are turned on.
local hazard                -- 0 or 1     - Flashing function when hazards are on.
local hazard_enabled        -- 0 or 1     - Indicates the hazards have been turned on
local highbeam              -- 0 or 1     - Tells if the high beams are turned on.
local lightbar              -- number     - Indicates the current lightbar mode
local lights                -- number     - Index of the current light mode (0 is off, 1 is lowbeams, 2 is highbeams)
local lights_state          -- number     - Index of the current light mode (0 is off, 1 is lowbeams, 2 is highbeams)
local lowbeam               -- 0 or 1     - Tells if the low beams are turned on.
local lowhighbeam           -- 0 or 1     - Tells if either the low or high beams are turned on.
local lowhighbeam_signal_R  -- 0 or 1     - Combines the lowhighbeam electrics with the signal_R electric. Lights up if either of those are on. Used for american style indicator/lights.
local lowhighbeam_signal_L  -- 0 or 1     - Combines the lowhighbeam electrics with the signal_L electric. Lights up if either of those are on. Used for american style indicator/lights.
local parking               -- 0 to 1     - Currently unused
local reverse_gear          -- 0 or 1     - Indicates a reverse gear is selected.
local signal_L              -- 0 or 1     - Flashes if the left turn signal or hazards are turned on.
local signal_R              -- 0 or 1     - Flashes if the right turn signal or hazards are turned on.
local signal_left_input     -- 0 or 1     - Indicates the left indicator is selected.
local signal_right_input    -- 0 or 1     - Indicates the right indicator is selected.
local turnsignal            -- 0, 1 or -1 - Varies depending on which turn signal is selected (right is 1, left is -1)

-- Vehicle Status

local airspeed              -- m/s        - Speed of the vehicle compared to the world.
local airflowspeed          -- m/s        - Speed of the vehicle compared to the airflow, taking into account wind.
local altitude              -- meters     - Altitude of the vehicle
local lowpressure           -- 0 or 1     - Indicates a tire is deflated
local oil                   -- 0 or 1     - Indicates the oil temperature is greater than 130°C
local rpmTacho              -- rpm        - Smoothed engine speed value for use with tachometers
local rpmSpin               -- Degrees    - Spin function based on engine RPM. Used for spinning pulley props.
local wheelspeed            -- m/s        - Speed of the car measured at the wheels.