The adiabatic approximation is used to describe the electron states of weakly-one-dimensional quantum wires. A clear order is evidenced in the longitudinal optical (LO) phonon mediated transition rates with respect to the quantum numbers of the confined states involved. The average single electron relaxation time from an excited level is shown either to increase or, surprisingly; to decrease as a function of the initial energy. The relaxation of an excited population is dynamically simulated, showing the wire size dependent accelerating and energy lowering effects of an additional phenomenological intrasubband thermalization.