A method for verifying speed data of an elevator car for overspeed monitoring of the elevator car, the method comprising: - obtaining at least one continuous speed data of the elevator car at two channels, - obtaining a zone speed data of the elevator car within at least one zone of an elevator shaft at two channels, the at least one zone of the elevator shaft is a door zone, wherein the door zone is as a zone extending from a lower limit below floor level to an upper limit above the floor level in which a landing and car door equipment are in mesh and operable, - generating a two-channel verified speed information by verifying the validity of the at least one continuous speed data by comparing the said at least one continuous speed data to the zone speed data at least at one channel, preferably at both channels, when the zone speed data is available, - generating a control signal for a safety device, if the comparison indicates a mismatch between the zone speed data and the at least one continuous speed data at least at one channel in which the comparison is provided, and - if the comparison indicates a match between the zone speed data and the at least one continuous speed data at each of the at least one channel in which the comparison is provided, the method further comprising: - comparing the verified speed information at each channel between each other by reciprocal comparison, and - generating the control signal for the safety device, if the reciprocal comparison indicates a mismatch between the verified speed information at the channels. - obtaining at least one continuous speed data of the elevator car at two channels, - obtaining a zone speed data of the elevator car within at least one zone of an elevator shaft at two channels, the at least one zone of the elevator shaft is a door zone, wherein the door zone is as a zone extending from a lower limit below floor level to an upper limit above the floor level in which a landing and car door equipment are in mesh and operable, - generating a two-channel verified speed information by verifying the validity of the at least one continuous speed data by comparing the said at least one continuous speed data to the zone speed data at least at one channel, preferably at both channels, when the zone speed data is available, - generating a control signal for a safety device, if the comparison indicates a mismatch between the zone speed data and the at least one continuous speed data at least at one channel in which the comparison is provided, and - if the comparison indicates a match between the zone speed data and the at least one continuous speed data at each of the at least one channel in which the comparison is provided, the method further comprising: - comparing the verified speed information at each channel between each other by reciprocal comparison, and - generating the control signal for the safety device, if the reciprocal comparison indicates a mismatch between the verified speed information at the channels. - comparing the verified speed information at each channel between each other by reciprocal comparison, and - generating the control signal for the safety device, if the reciprocal comparison indicates a mismatch between the verified speed information at the channels.