Abstract: An obstruction safety detector having coactive spokes and flexible electrical conductors, mounted relative to dual tires of a vehicle for flash signalling the presence of an obstruction such as a stone, between adjacent tires forming the duals or tandem duals, including a chassis-mounted flexible detector adapted to deflection by the obstruction between rolling tires. The detector, upon deflection, closes an electrical switch in an electrical signalling circuit, which when thus closed, transmits intermittent current to a signal on the instrument panel of the vehicle, thereby warning of the obstruction.