A lighting apparatus includes a primary power supply, a primary lighting unit, a control unit, a secondary lighting unit, a light sensor, and a back-up power supply. The control unit is connected to the primary power supply, the primary lighting unit, the secondary lighting unit, the light sensor and the back-up power supply. The primary lighting unit includes at least one high-power lamp controlled by the control unit. The secondary lighting unit includes at least one low-power high-intensity light source. The light sensor generates a light signal corresponding to intensity of ambient light. The control unit enables operation of the secondary lighting unit when the primary lighting unit is deactivated during poor ambient light conditions, and further enables supply of power from the back-up power supply to the secondary lighting unit to activate the latter when power failure of the primary power supply occurs.