Large trucks can have two times the observation angle as passenger vehicles when seen from the same distance. There’s much less reflected light available for these drivers to see road signs. That’s why for large vehicles, high-quality retroreflective truck signs are vital as they would return more light in a larger cone of reflectivity. In a typical passenger vehicle, the light from headlights, hitting on a sign at 300-feet, will return at an angle of about 0.5-degree. This is called the angle of observation. In an SUV or pickup truck, this angle increases to nearly 0.6 degrees. In a semi-trailer truck where the driver is distanced furthermore from the headlights, the observation angle increases to approximately 1.2 degrees.