The collision of OH with the oxygen molecule is studied by the trajectory simulation technique on the model; potential energy surface of OH + O-2 --> O-3 + H chemical reaction. Although the reaction channel is closed, we aim to demonstrate that the L-shape of the OH + O-2 valley leads to the effective coupling of OH(upsilon) vibration with the relative motion of collisional partners and therefore explains the high value of the vibrational relaxation rate constant observed experimentally, The characteristic feature of the mechanism considered is the predominance of one-quantum relaxation for low and multiquantum transitions for high OH vibrational levels. To estimate state-to-state vibrational relaxation rate constants, the method of dynamical corrections of transition state theory is used. The expression for the rate constant consists of a transition state term and a correction factor, determined in two-dimensional classical trajectory calculations. We also demonstrate the instability of motion on the potential energy surface with the L-shape valley, resulting from the scattering of the trajectory on the "corner" of the potential energy surface and the presence of regular and chaotic motions.