An escalator system comprising: a first member which is a first stationary member, a handrail belt, a handrail belt drive assembly operationally connected to the first member and the handrail belt, the assembly comprising a sheave (240, 240A, 240B) mounted proximate the first member on which the handrail belt is driven, a sensor (250, 250A; 250B) mounted to the first member proximate to the sheave (240, 240A, 240B), characterized by the sensor (250, 250A; 250B) sensing a relative transverse position of the handrail belt relative to the sheave (240, 240A, 240B), and a controller communicating with the sensor (250, 250A; 250B), wherein when the handrail belt is moving from rotation of the sheave (240, 240A, 240B) the controller is configured to receive data from the sensor (250, 250A; 250B), determine when the handrail belt moves transversely relative to the sheave (240, 240A; 240B), compare the transverse movement with a reference value, provide a predetermined response when the transverse movement diverges from the reference value by more than a predetermined amount. a first member which is a first stationary member, a handrail belt, a handrail belt drive assembly operationally connected to the first member and the handrail belt, the assembly comprising a sheave (240, 240A, 240B) mounted proximate the first member on which the handrail belt is driven, a sensor (250, 250A; 250B) mounted to the first member proximate to the sheave (240, 240A, 240B), characterized by the sensor (250, 250A; 250B) sensing a relative transverse position of the handrail belt relative to the sheave (240, 240A, 240B), and a controller communicating with the sensor (250, 250A; 250B), wherein when the handrail belt is moving from rotation of the sheave (240, 240A, 240B) the controller is configured to receive data from the sensor (250, 250A; 250B), determine when the handrail belt moves transversely relative to the sheave (240, 240A; 240B), compare the transverse movement with a reference value, provide a predetermined response when the transverse movement diverges from the reference value by more than a predetermined amount. a sheave (240, 240A, 240B) mounted proximate the first member on which the handrail belt is driven, a sensor (250, 250A; 250B) mounted to the first member proximate to the sheave (240, 240A, 240B), characterized by the sensor (250, 250A; 250B) sensing a relative transverse position of the handrail belt relative to the sheave (240, 240A, 240B), and a controller communicating with the sensor (250, 250A; 250B), wherein when the handrail belt is moving from rotation of the sheave (240, 240A, 240B) the controller is configured to receive data from the sensor (250, 250A; 250B), determine when the handrail belt moves transversely relative to the sheave (240, 240A; 240B), compare the transverse movement with a reference value, provide a predetermined response when the transverse movement diverges from the reference value by more than a predetermined amount. receive data from the sensor (250, 250A; 250B), determine when the handrail belt moves transversely relative to the sheave (240, 240A; 240B), compare the transverse movement with a reference value, provide a predetermined response when the transverse movement diverges from the reference value by more than a predetermined amount.