This nomograph displays relative rotational speeds of the planetary elements. The relative spacing of the speed lines for the various elements is related to the planetary gear ratio.  Since vehicle speed is ring gear speed times a constant (final drive ratio and tire size), the rightmost line is indicative of both ring gear speed and vehicle speed.  At rest, engine off, all speeds are zero.

To accelerate the vehicle from rest with the engine off, power is applied to the motor from the battery.

Note generator speed is negative in this case.  For any given steady state vehicle speed, engine speed can be adjusted by varying generator speed.

To start the engine, generator speed is increased electrically, causing an increase in engine speed.  Adding fuel and spark causes combustion to begin and power to be produced.

Note this is also possible at non-zero vehicle speeds.  Because there is no reverse gear, vehicle reverse is a motor only drive mode.
 

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