The category "<speed_command>" can be expressed as follows:

<speed_command>

<change_parameter> <speed_descriptor> by <speed>

<change_parameter> <speed_descriptor> to <speed_setting>

<set_attribute> <speed_descriptor> to <speed_setting>

slow down

slow down by <speed>

slow down to <speed>

speed up

speed up by <speed>

speed up to <speed>