The effects of using a vision enhancement system when driving a car at night, especially those based on infrared image information are reviewed. Principles and a short technical background are given for night vision systems in cars. The following issues are discussed: Human vision at night, infrared image information, and human factors of night vision systems. A proposal is made for using the terms indirect viewing panel and direct viewing panel instead of the terms head up display and head down display. The advantages for older drivers are pointed out. Methodological aspects of how to study human factor aspects of night vision systems are also reviewed. Measures to be used as dependent variables are suggested: Speed, time to collision, eye movements, reaction time, lateral position of the car on the road, and the workload of the driver. Recommendations, based on visual ergonomics, taking into account different visual fields for where to put the image are given. Here suitable image distances, locations, and sizes are discussed.