Example drive systems for handrails of walkways and moving stairs may comprise a plurality of carriages. In some examples, each carriage may comprise a body with several leading rollers that roll along a guide that defines a handrail path. The carriage may further comprise a locking/release mechanism for selectively coupling the carriage to a drive chain of the handrail. The locking/release mechanism may comprise a hook configured to move between an engagement position wherein the carriage is coupled to the drive chain and a disengagement position wherein the carriage is uncoupled from the drive chain. In some cases, a position of the hook may be controlled by a wheel that travels along a cam profile.