Learn English – Convert passive voice to active voice with verb “to know”

An intransitive verb like walk cannot sustain ordinary passivization because it has no Object which can be cast as the Subject of a passive clause.

However: if the active utterance contains a preposition phrase as predicative complement, the object of the preposition can in some circumstances be cast as Subject.

Somebody slept in this bed. → This bed has been slept in.

But this works semantically only if the action of the verb has some evident effect on the object of the preposition. The example above, for instance, makes sense because a viewer might deduce the sleeping from some disarrangement of the bedclothes.

But what about this?

The road is being slowly walked on.

It's difficult to conceive circumstances in which that would be a sensible utterance—perhaps a Dungeons and Dragons game in which the dungeonmaster describes visible effects (such as footprints) of an invisible character walking on the road?

If you want to retain the future continuous in the passive transformation, you can use "getting" instead of "being":

My clothes will be getting washed by my mother.

"will be being" is a combination a speaker of American English is not likely to hear in a lifetime.