We investigate the unexplored physics of slow light effect in resonance induced transparent grating waveguide structures. We show that with a simple three-layer thin-film structure, a narrow transparent window can be obtained, enabling substantially slow down the speed of out-of-plane propagation of light. Further, we numerically demonstrate an active slow light device that potentially achieves high-speed control of slow light at the optical communication band. This work paves a way for the design of functional devices, such as slow-light chips, switches, and modulators functioning in optical and infrared regimes. [ABSTRACT FROM AUTHOR]