A traction motor without gearing could open up some real possibilities. For instance if you could eliminate the solid axle and incorporate the strength and rigidity of the truck into the body of the car a really low floor streetcar would be possible. I am talking about a suspension somewhat like the front axle assembly of an automobile. There would be wheel wells of course and you might have to access the motors thru the floor but everything else would be at curb level.

If each wheel were motorized separately and spun separately that would go quite a ways to alleviating wheel squeal, I would think. And you should be able to reduce vehicle weight.