A safety device for a vehicle fitted with a seat belt having at least a lap portion which, in use, extends across the user's upper legs has two spaced apart guides (22) through each of which the lap portion of the belt extends, the guides (22) being located on respective sides of the user's upper legs. In one embodiment, the safety device includes a pad or cushion (10) which, in use, is placed on the vehicle's seat and upon which the user sits. The guides (22) may be anchored to respective sides of the vehicle seat, or the pad or cushion (10), and consist of a sheet of fabric folded in half which is releasably closeable along its free edges by a fastening such as VELCRO (Registered Trade Mark).