Two experiments were conducted to develop symbols for seven automobile controls and displays (heater, air conditioner, fresh air vent, radio volume, radio tuning, exterior lamp failure, and tire pressure) and answer several related questions.
In the first, 43 drivers drew pictures they thought should be used as symbols for the items in question. Based on their suggestions the author designed several candidate symbols for each function.
In the second, 62 drivers rated how well each candidate's intended meaning was understood. For many functions a “best” symbol was found, often one which differed from that currently used by the automobile manufacturers.