This paper presents a simulation and comparison of two different infra-red imaging systems in terms of their use in automotive collision avoidence applications. The first half of this study concerns the simulations of an “cooled” focal plane array infra-red imaging system, and an “uncooled” focal plane array infra-red imaging system. This is done using the United States Army's Tank-Automotive Command Thermal Image Model - (TTIM). Visual images of automobiles - as seen through a forward looking infra-red sensor - are generated, by using TTIM, under a variety of viewing range, and rain conditions. The second half of the study focuses on a comparison between the two simulated sensors. This comparison is undertaken from the standpoint of the ability of a human observer to detect potential (collision) targets, when seeing through the two different sensors. A measure of the target's detectability is derived for each sensor by using the United States Army's Tank-Automotive Research Development and Engineering Center Visual Model (TVM).