The car is 11 inches in width on the front of the shirt.  Including the street signs its close to 12 inches in height.
 
The top street sign is 2 inches.  The bottom street sign is 4 inches.  If you add St/Ave/Blvd then the names have to be smaller to fit them inside the street signs. 
 
If you pick the dark gray shirt with a black car you will barely be able to see the car.