A popular misconception is that good aerodynamic shapes have narrow leading edges and gradually get larger. However, the opposite is true. A good aerodynamic shape is curved but relatively blunt on the windward side and gradually gets slender on the leeward side, ending with as small a size as possible. Think of the cross section of a airplane wing, the shape of the fuselage of an aircraft, or the shape of most fish. Additionally, good aerodynamic shapes have no sharp corners or edges and minimal protruding parts. The importance of shape on drag is dramatic. For example, the attached file shows a cylinder and an airfoil that have the same aerodynamic drag at high velocities. It is quite amazing how much difference it makes. That said, aerodynamic drag is a relatively minor portion of the losses that cars experience at speeds lower than freeway speeds.

Hai Raji,

I strongly agree with the answer given by Larry Baxter, apart from that the frontal area of a car is called as Crumble zone. When we are doing aerodynamic design we should consider parameters required for the crumble zone, in case of automobiles. If this is case of trial it is not an essential parameter but considering this too will make better result.

Do well

All the best

 Then Why do fast trains like bullet trains have narrow frontal regions when compared to normal trains. Is it right when I compare the body design of a four wheeler with that of a train?

At very high velocities, the frontal shape of the vehicle affects stability and control. Both high-speed cars and trains are shaped so the air flow keeps them on the ground/track rather than allowing a large wedge of air to flow under them, which tends to lift them off the ground. 

Another point is, that air resistance is proportional to the flow resistance coefficient, the projected front surface and the square of the velocity. Thus, very fast vehicles like fast trains or race cars need to focus on small surfaces more then regional trains or the bionic car you mentioned. Greetings.

Dear Mr. Larry L.Baxter,

Could you please explain your answer with an image or an illustration? What does the narrow frontal region has to do with air flow under the vehicle?

The issue is that most of the air flows over the top of the vehicle, pushing the front of the vehicle down and increasing traction. If most of the air flows under the vehicle and lifts the front, the vehicle loses traction and, in an extreme case, becomes partially airborne or flips the front of the vehicle up (as is a common scenario with high-speed boats). 

Thank you sir for answering my queries.

It affects the air resistance and the drag coefficient of a moving vehicle