Approximate cumulative reaction probabilities have been calculated from two empirical rate equations: one is the 3-parameter rate equation, AT(n) exp(-E/k(B)T), and the other is the modified Arrhenius equation, A'exp(-E-0/k(B) rootT(2) + T-0(2)) proposed in Chem. Phys. Lett. 160 (1989) 295, for expressing the rate constants at low temperatures. Numerical calculations were made for the D + H-2 --> DH + H reaction. It is shown that this reaction occurs mainly through tunneling at 200 K, and that the 3-parameter rate equation involves the tunneling effect along with the correction at high temperatures. (C) 2004 Elsevier B.V. All rights reserved.