The Night Vision and Electronic Sensors Directorate's current time-limited search model, which makes use of the targeting task performance (TTP) metric to describe imager quality, does not explicitly account for the effects of clutter on observer performance. The masked target transform volume (MTTV) clutter metric has been presented previously, but is first applied to the results of a vehicle search perception experiment with simulated thermal imagery here. NVESD's Electro-Optical Simulator program was used to generate hundreds of synthetic images of tracked vehicles hidden in a rural environment. 12 observers searched for the tracked vehicles and their performance is compared to the MTTV clutter level, signal-to-clutter ratios using several clutter metrics from open literature, and to the product of target size and contrast. The investigated clutter metrics included the Schmeider-Weathersby statistical variance, Silk's statistical variance, Aviram's probability of edge detection metric, and Chang's target structural similarity metric. The MTTV was shown to better model observer performance as measured by the perception experiment than any of the other compared metrics, including the product of target size and contrast.© (2010) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.