Why do many trailer use wind deflectors on the top of their cabs?

Many trailers use wind deflectors on the top of their cabs to improve aerodynamics and reduce drag while driving. By directing airflow smoothly over the trailer, these deflectors help minimize turbulence, which can lead to better fuel efficiency and increased stability on the road. Additionally, they can contribute to overall safety by preventing wind from lifting the trailer at high speeds. Overall, wind deflectors enhance the performance and efficiency of heavy vehicles.