A system, self-contained operational entity, that provides vehicle approach speed monitoring, for at least one lane leading to a red light of a signal-controlled roadway intersection, to measure vehicle deceleration rate approaching said red light and methods of warning, visually and audibly, for at least one lane leading to said light of said intersection, to gain vehicle operator's attention to prevent intentional and/or unintentional red light violations at said intersection. Said system, utilized in groups of at least two, also avoids collisions within said intersection due to said violations by warning, visually and audibly, to vehicle operators receiving a green light at same said opposing intersection to slow immediately and look for possible vehicle running red light against their traffic flow and if clear proceed normally.