A commercial semi truck driver must maintain a proper speed at all times. Determining a safe speed for a heavy vehicle depends on many critical factors.   Proper speed factors for semi trucks: Traffic conditions; Road conditions and construction; Weather conditions, especially rain, snow or ice; Visibility that may be affected by weather and precipitation, sun glare, or the condition of the truck. The skill and experience of the truck driver; The load weight and type, and the load safety; The Posted Speed Limit and traffic flow; and The shape of the road itself, including curves and grades. Speed control means operating at the proper speed for all road and traffic conditions. A proper speed allows for the driver to