1. A method of providing a road departure warning alert in a vehicle comprising: creating a road texture model based on a vehicle image received from a vehicle camera, the road texture model classifying each of a plurality of portions of the vehicle image as road or non-road; smoothing the road texture model by: identifying outlier portions of the vehicle image, wherein each outlier portion comprises an image portion classified as non-road and surrounded by a threshold number of portions of the vehicle image classified as road; and re-classifying the identified outlier portions as road; retrieving map imagery based on an initial vehicle location estimate; determining a refined vehicle location using visual egomotion based on the vehicle image and the map imagery by: aligning 3D features between the vehicle image and each map image in the retrieved map imagery; selecting a map image based on the aligned 3D features; determining a displacement between a location associated with the selected map image and a corresponding location associated with the vehicle image; and applying the determined displacement to the initial vehicle location estimate to determine the refined vehicle location; creating a road boundary model describing the edges of the road on which the vehicle is located based on the smoothed road texture model and the refined vehicle location; creating a road departure model based on the road boundary model and vehicle odometry information; and warning a vehicle operator based on the road departure model.