This paper considers a decentralized control problem for suppressing a traffic jam phenomenon in a cyclic traffic flow. To explain such a phenomenon, the so-called optimal velocity model is proposed. The model exhibits the characteristics of a vehicle controlled by a human driver. In the previous work by Yamamoto and Sakaguchi in 2011, it was shown that a washout control method is effective to suppress a traffic jam which occurs in a kind of vehicular traffic flows by a numerical simulation. In this paper, we first reproduce a traffic jam observed in a cyclic traffic flow where many cars run on a single track in the high density by using several Lego cars which realize the optimal velocity model by using LEGO mindstorm NXT. Then, we apply washout control to each Lego car and show how the traffic jam vanishes.