The kinetics of car clustering in a single-lane highway traffic flow is described in terms of a Boltzmann-like kinetic equation. Effect of car acceleration upon car clustering is studied by deriving the velocity distribution of cars. The discrete version of the kinetic equation is presented to solve numerically its equation. The time evolutions of velocity distributions are calculated by numerical method. The velocity distributions in a steady state are also derived numercally by taking into account deceleration. It is shown that the velocity distribution becomes broader and broader with increasing acceleration. It is found that the clustering, acceleration and deceleration have an important effect on the velocity distribution of cars.