In order for a vehicle to double its kinetic energy, the velocity of this vehicle needs to be increased by a factor of 4. While its true that kinetic energy is proportional to the square of the velocity, the equation would read as KE2=KE1(v2^2/v1^2). This would require that the vehicle velocity be increased to 4 times its initial velocity.
For example, if a vehicle was travelling at 10 m/s, the vehicle would need to increase its velocity to 40 m/s to double its kinetic energy.
