Removing the CPL filter will allow for faster shutter speeds as it reduces usually about 2-3 stops of light allowed in. Cleaning the windshield while helpful, is not blocking THAT much light intensity, unless it was mud. Night itself, digital capture physics are the main problem. Freezing motion in the dark is not always possible & even during the day, depending on the light volume & speed & angle of the subject. Dashcams are AIDS, not 100% perfect capture devices in all situations. Even my digital SLR with really expensive lenses & my 40 years of professional experience CANNOT freeze motion of every moving object in every condition, especially at night. I would never expect a $100 to $10,000 video camera to do it. At night, sometimes the motion & angle are perfect to be captured sharp, but most often they would not be. Just like once in hundreds or thousands of captures, I can get a sharp image with my 500 mm lens hand held at 100 ISO in late afternoon. At night though, likely never.