First of all, AE does not have an Isometric camera that will render. This means that you will either have to fake it with an incredibly long lens or create your isometric artwork and animate that. All 3D layers are flat planes so creating a 3D car would be easier in a 3D app. If the design is not too complex then you could use C4D lite that comes with AE. You may even be able to find a model somewhere that would do or could be easily modified. Getting the Car to move properly in AE's 3D world takes a bit of work and you will probably need to spend several hours learning how to use C4D Lite and Cineware. The other option, which will cost you some money, is to use Element 3D or other 3rd party 3D plug-ins.
If this were my project and I really needed Isometric 3D streets and a car I would just use Blender. htto://blender.org. It is an open source fully functional 3D app that can easily create your project. It's not that you could not do the project in AE, but if you are not already very familiar with AE;'s 3d space, with C4D Lite or one of the 3rd party 3D plugins, you'll probably spend as much time learning how to do it in AE as you would in Blender and you'll still need to figure out how to fake the isometric look.
Thank you for your reply - you are absolutely right, ive just tried opening a SVG file in after effects and its obviously not supported. I had more luck in animate cc - I didnt really want to go outside of adobe creative cloud apps unless I need to.
I think I can achieve what I need in animate CC but would be interested to see what you think? Regards, John