It is proved that every two-way reversible finite automaton (2RFA) with n states can be simulated by a partial one-way deterministic finite automaton (1DFA) with φ(n) states, where φ is a certain integer function of growth rate φ(n)=O((n2)n/2+3/2). Furthermore, it is shown that exactly φ(n) states are necessary in the worst case, with witness languages defined by sweeping reversible automata over a 4-symbol alphabet. The second result of the paper is a new lower bound 2n+2nlnn+o(1) on the complexity of transforming a deterministic two-way finite automaton (2DFA) to a 2RFA, cf. the known upper bound of 4n+3 states.