[en] A radiation monitor has been developed that will scan each vehicle leaving the Clinton P. Anderson Los Alamos Meson Physics Facility site. If an increase in radiation level is sensed, an alarm light and a Klaxon horn are activated, inviting the driver to return to the Health Physics office for check. A photograph showing the vehicle license number is also taken. A radiation source that doubles the detector count rate when stationary will cause an alarm at vehicle speeds up to about 24 km/h (15 mph). The technique used to prevent false alarms because of radiations from nearby buildings or from plumes of low-level radioactive gas is described. 9 figs