Effects of the interladder one-particle hopping, t ⊥ , on the low-energy asymptotics of a weakly coupled Hubbard ladder system have been studied, based on the perturbative renormalization-group approach. We found that for finite intraladder Hubbard repulsion, U , there exists a crossover value of the interladder one-particle hopping, t ⊥ c . For 0< t ⊥ < t ⊥ c , the spin gap metal (SGM) phase of the isolated ladder transits at a finite transition temperature, T c , to the d -wave superconducting (SCd) phase via a two-particle crossover. In the temperature region, T < T c , interladder coherent Josephson tunneling of the Cooper pairs occurs, while the interladder coherent one-particle process is strongly suppressed. For t ⊥ c < t ⊥ , around a crossover temperature, T cross , the system crosses over to the two-dimensional (2D) phase via a one-particle crossover. In the temperature region, T < T cross , the interladder coherent band motion occurs.