Adverse　weather　such　as　fog　will　reduce　drivers＇　visual　recognition　ability,　and　important　visual　information　in　the　driving　will　be　weakened　and　even　lost,　which　brings　risks　to　driving　safety.　This　paper　sets　out　to　explore　causes　for　the　decline　in　driving　visual　ability　in　foggy　sections　at　night　based　on　drivers＇　visual　recognition　demand　mechanism.　The　purpose　is　to　study　the　influence　of　light　source　characteristics　on　visual　distance　under　open　traffic　conditions.　Through　an　outdoor　visual　recognition　test,　data　were　collected　on　the　visual　recognition　distances　of　12　car　drivers　to　standard　gray　small　targets,　under　different　light　source　characteristics　and　meteorological　visibility　conditions.　Results　revealed　that　the　latter　conditions,　along　with　illuminance　and　correlated　color　temperature　affected　drivers＇　visual　recognition　ability　in　low　meteorological　visibility　sections　at　night.　At　the　same　illuminance　and　meteorological　visibility,　a　light　source　with　high　correlated　color　temperature　could　improve　visual　distance.　The　multivariate　power　function　model　of　meteorological　visibility,　illuminance　at　the　target　and　driver＇s　visual　distance　in　foggy　areas　were　obtained　by　fitting.　The　research　methods　and　conclusions　could　provide　technical　reference　for　improving　traffic　visual　distance　at　night,　and　thus　help　lay　a　foundation　for　road　construction　and　traffic　control　technology　in　foggy　areas.