A controller for operative connection to a power assisted transport vehicle that is at least partially directed by a human operator in physical contact with the vehicle, the controller including: a contact surface with a deadman switch, a first sensor and a second sensor each responsive to manual actuation of the contact surface, each sensor having a respective first sensor output signal and a second sensor output signal, and a signal processing means adapted to process the first and second output signals, and control the mode of operation of the controller in accordance with the state of the deadman switch.