It looks like a nice start but I see some problems there.
Most importantly, there's a lot of double black lines: most notably on the doors and the equipment below the cabin.
Secondly, it seems to have no shading at all.
The double lines on the doors were merely there to denote extra width, where three lines would be deemed too wide and one line too narrow. However, I can understand where you're coming from regarding the underfloor equipment, and the shading was definitely too subtle (only being on the bumpers).