This is a model I did off the bat of a tutorial. I wasnt happy with the progress of my automobile models so I sought to improve my skills. The tutorial was based on chris plush's dvd camero tutorial at cgmasters.net. I followed the tutorial religiously until the point where adding the materials as i modelled in cycles and the tutorial is in internal blender. I posted this to show my progression and development in understanding automobile design and would advise that for anyone seeking to develop ones skills in such an area should start with such a tutorial. I decided to customise the model and turn it into a police car. Hope you like it thanks.

Please note that for recommended render , render at 1500 samples and at subsurf level 2. Also note by default the simplify function is turned on. If you discover the subsurf levels dont change then uncheck the simplify button which will then allow you to subsurf parts individually.thankyou