The　influence　of　twin-box　girder　attachments　on　the　driving　wind　environment　of　a　long-span　coastal　bridge　under　crosswind　was　experimentally　studied　in　a　boundary　layer　wind　tunnel.　First,　the　particle　image　velocimetry　(PIV)　technique　and　anemometers　were　used　to　determine　the　optimal　PIV　window　size.　Then,　the　effects　of　attachments　and　vehicles　on　average　wind　speed,　turbulent　kinetic　energy,　Reynolds　stress,　and　equivalent　wind　speed　reduction　coefficient　on　the　driving　wind　environment　were　analyzed.　Results　indicate　that　bridge　attachments　alter　both　the　magnitude　and　distribution　of　average　wind　speed　on　the　windward　side　of　the　vehicle.　Turbulent　kinetic　energy　peaks　were　observed　near　the　windward　side　of　attachments,　particularly　in　the　wake　region　above　the　vehicle.　Reynolds　stress　peaks　were　primarily　located　on　the　windward　side　of　the　attachments;　increasing　the　height　of　the　attachments　expanded　the　peak　area　above　the　vehicle　while　reducing　the　wake　region＇s　area.　The　coefficient　of　equivalent　wind　speed　reduction　provides　a　reasonable　quantification　of　changes　in　the　driving　wind　environment.　However,　the　difference　between　conditions　with　and　without　the　vehicle　was　significant,　suggesting　that　practical　wind　barrier　solutions　should　prioritize　aerodynamic　measurements　of　vehicles　behind　wind　barriers.　　©　2026　World　Scientific　Publishing　Company.