Use a circular polarizing filter on the lens to cut windshield reflections in daylight. Rotate it while framing the shot to find the position that minimizes glare. This is the main tool for reducing reflections from the glass.

A polarizer usually won’t do much for direct headlight glare, so also light the driver from inside or from the side. Soft, diffuse light aimed at the subject can help the driver read brighter than the reflections. If practical, an open side window may make lighting easier.

If headlights are causing problems, try balancing the shot by increasing light on the driver rather than expecting the filter to fix the lamps.

Most importantly, prioritize safety. Filming moving vehicles should be carefully planned and controlled; professional productions often use controlled roads or vehicle rigs rather than improvising on open roads.