Answer
We cannot observe the de Broglie wave associated with the moving car.
Work Step by Step
The matter wave or de Broglie wave associated with moving particle is given by
$\lambda= \frac{h}{mv}$
where $h $ is planks constant ,$m$ is mass of particle and $v$ is speed of the particle.
Typically mass of a Car is around 1000 kg .assuming it to be of the order of $10^{3}kg$
Maximum speed of the normal car is 250 km/hr=69.4 m/s assuming it tobe of the order of $10^{2}m/s$
so for normal car putting these value in above equation will give
de Broglie wavelength $\lambda= \frac{6.63\times10^{-34}J-s}{10^{3}kg\times10^{2}m/s}$
$\lambda=6.63\times10^{-39}m$
$\lambda=663\times10^{-28}nm$
which is $10^{28}$ times shorter than the wavelength of RED light. so it is not observable.
