1. A system for estimating a time-to-contact an object using vision and range sensor data for autonomous navigation, comprising: one or more processors and a memory, the memory having executable instructions encoded thereon, such that upon execution of the instructions, the one or more processors perform operations of: segmenting an image from a monocular video into multiple object regions of interest, the image being of a scene proximate a mobile platform; calculating time-to-contact (TTC) values by estimating motion field and operating on image intensities; generating a two-dimensional (2D) TTC map by estimating average TTC values over the multiple object regions of interest; fusing range depth data from a range sensor with the image to generate a three-dimensional (3D) TTC map; and generating a range-fused TTC map by averaging the 2D TTC map and the 3D TTC map.