Hi @Hassaan_Sohail It was a bug and is solved in JME 3.1 SDK.
Actually that blue box on your car is not a collision shape it is just a bounding box. And it seems you are using JME 3.0 SDK yet. It was a bug and now is fixed on JME 3.1 SDK
See
Please download JME 3.1 SDK from
Good Luck