Some night vision systems have sensors mounted on the sides of the helmet with visual output projected onto a display in front of the operator’s eyes. This arrangement produces a situation of hyper-stereopsis in which binocular cues available to the operator are exaggerated so that distances around fixation are magnified. We used computer-generated graphics and a z-screen and passive polarised glasses to simulate hyper-stereopsis to measure its effects on (a) perceived slope and (b) estimates of time to contact (TTC), to see if hyper-stereoscopic cues influenced slope and TTC judgements, over and above those from monocular cues (e.g., texture gradient, and optic flow). We found that slope was overestimated under conditions of hyper-stereopsis and TTC judgements were underestimated. Though, we observed that the miss-estimations were less than would be expected given the 4-times interpupillary distance employed. These distortions in perceived slope and judged TTC support reports of visual distortions from pilots who use these devices in the field.