Is it ok to block up an air vent in a bedroom?

your Friends are right ...bad idea ..its a bedroom vent ..and the fact that you are complaining about road noise tells me you don't open your window ...another bad idea ...just sit in your car for 5 minutes with all windows closed ..they will soon mist up ..with condensation from your breath ..bedrooms are the same ..except you get mould ...you must ventilate ..you will sleep better for it