will or would

[diamondcutter]

The bus pulled up. Mrs. Kormel, the bus driver, pushed a button and made the little STOP sign pop out the side of the bus so the cars on the street will stop. We call it the magic STOP sign. That thing is cool.

Source: Mrs. Kormel Is Not Normal, Dan Gutman

To agree with the past tense of the other verbs: pushed, made, should the modal verb “will” be “would” ?

 

[tedmc]

It could be either. Backshifting of tense is not a must.

 

[5jj]

To agree with the past tense of the other verbs: pushed, made, should the modal verb “will” be “would” ?

Yes.

 

[jutfrank]

I think the writer deliberately chose will as opposed to would because so the cars in the street will stop doesn't relate to the purpose of Mrs Kormel's action but to the purpose of the stop sign generally.

 

[Tdol]

And things like the magic STOP sign make the present OK to me.