A braking system for a towed vehicle, comprising: a first mechanical coupling between the towed vehicle and a towing vehicle by which the towing vehicle is able to tow the towed vehicle; a brake for applying a braking force to a wheel of the towed vehicle; an actuator for actuating said brake, wherein the actuator is mechanically coupled to the brake by a second mechanical coupling, said second mechanical coupling being configured to transmit a force to the brake by which force the brake can be operated and preferably comprising a brake rod; a brake signal receiver for receiving a brake signal from the towing vehicle, said brake signal indicating whether a braking system of the towing vehicle has been activated or not; and a controller for controlling the actuator; wherein the towed vehicle braking system further comprises a coupling force determination unit that is mechanically coupled to the first mechanical coupling, said coupling force determination unit being configured to output a coupling signal that is indicative for a towing force that is exerted by the towing vehicle onto the towed vehicle, and vice versa, through the first mechanical coupling, said controller being configured for controlling the actuator in dependence of the coupling signal and the received brake signal to reduce the towing force; wherein the coupling force determination unit comprises a force sensor for measuring the towing force, said force sensor being mechanically coupled to the first mechanical coupling; characterized in that the force sensor comprises: a force sensing spring (206, 207) that is arranged in between the first mechanical coupling and a frame of the towed vehicle; a position determination unit for determining the amount of extension or compression of the force sensing spring; and a force calculation unit for calculating the towing force based on a spring constant of the force sensing spring and the determined amount of extension or compression; wherein the force sensor further comprises a damper for damping the relative movement between the first mechanical coupling and the frame of the towed vehicle. a first mechanical coupling between the towed vehicle and a towing vehicle by which the towing vehicle is able to tow the towed vehicle; a brake for applying a braking force to a wheel of the towed vehicle; an actuator for actuating said brake, wherein the actuator is mechanically coupled to the brake by a second mechanical coupling, said second mechanical coupling being configured to transmit a force to the brake by which force the brake can be operated and preferably comprising a brake rod; a brake signal receiver for receiving a brake signal from the towing vehicle, said brake signal indicating whether a braking system of the towing vehicle has been activated or not; and a controller for controlling the actuator; wherein the towed vehicle braking system further comprises a coupling force determination unit that is mechanically coupled to the first mechanical coupling, said coupling force determination unit being configured to output a coupling signal that is indicative for a towing force that is exerted by the towing vehicle onto the towed vehicle, and vice versa, through the first mechanical coupling, said controller being configured for controlling the actuator in dependence of the coupling signal and the received brake signal to reduce the towing force; wherein the coupling force determination unit comprises a force sensor for measuring the towing force, said force sensor being mechanically coupled to the first mechanical coupling; characterized in that the force sensor comprises: a force sensing spring (206, 207) that is arranged in between the first mechanical coupling and a frame of the towed vehicle; a position determination unit for determining the amount of extension or compression of the force sensing spring; and a force calculation unit for calculating the towing force based on a spring constant of the force sensing spring and the determined amount of extension or compression; wherein the force sensor further comprises a damper for damping the relative movement between the first mechanical coupling and the frame of the towed vehicle. a force sensing spring (206, 207) that is arranged in between the first mechanical coupling and a frame of the towed vehicle; a position determination unit for determining the amount of extension or compression of the force sensing spring; and a force calculation unit for calculating the towing force based on a spring constant of the force sensing spring and the determined amount of extension or compression; wherein the force sensor further comprises a damper for damping the relative movement between the first mechanical coupling and the frame of the towed vehicle.