Where are you? Give nearest large city and USDA growing zone.

A tall narrow shrub might work better than a tree, and a fence might work as well. Add in a photo of the space to help get suggestions.

Providence Rhode Island. I will take some pictures tomorrow in the sunlight. Thanks for your response.

I don’t think that 4 feet is wide enough for a privacy tree. Is the window on the first or 2nd floor?

It's on the 1st floor. A fence was my original thought but I'd much rather look at something green than a fence. I suppose maybe a large plant or tree could work on the inside as well? The window faces east and gets plenty of sunlight.

Depending on where you live, it could be possible to erect a lattice screen and grow an evergreen vine on it. But most evergreen vines require a pretty mild climate. Can you tell us where you live?

Put in a fence and then plant something green in front of it.

looking forward to the pix ....

how high is the window... top and bottom ... how much elevation or height will you need... to accomplish your goal ...

and will your neighbor object to a tree overhanging his driveway ...

i cant really think about any TREE ... that in tree time.. decades... will fit into a 4 foot space .... and stay in that space ...

and keep in mind.. trees never really stop growing ... both up and out ... its going to be a tough space ...

you might have to look into a shrub.. whcih can be maintained ... thru annual pruning ...

pix plz ...

ken