Understanding PerspecitveProjection

Apoligies In advance if this post appears nonsensical but I’m learning about 3D and havent come to grips with full terminology and concepts yet.

I am trying to build a 3D world from AS3 2.5D principles.
In the world a car navigates though the world. Thus the driver looks out the windscreen at their view of the world.
I have decided to try using perspectiveProjection for this.
Are these ideas correct for each frame ?
The presented view is created with moving the x y and rotation of the map.
The
projectionCenter
would then be set to a similar Point xy as the position.
The focallength needs to be reset in accordance with the distance of the boundary and or walls/
The **focalWidth **is only used for ‘effect’ in showing speed jumps…

So far I have been getting both weird and wonderful results, but am unsure how all the perspectiveProjection properties interact.

Thus any help welcome.