CRS 42-4-1007 mandates that drivers not change lanes until they 'first ascertained that such movement can be made with safety.' When determining whether a motorist followed traffic regulations, courts will consider the 'totality of the circumstances.' The statute does not provide technical details such as how many feet or car lengths of space drivers should have before switching lanes at a safe distance. But before attempting a lane change, motorists should always rely on turning, their side- and rear-view mirrors, and sensors (if their vehicle has them). And they should use their turn signals with their tail lamps before switching lanes. Furthermore, the lane change should be quick so the driver is in between lanes for as little time as possible. As the statute states, 'a vehicle shall be driven as nearly as practicable entirely within a single lane[.]' The statute also prohibits using the shoulder lane when overtaking vehicles. Left turns should only happen from left lanes. And it requires drivers to obey any official traffic control devices that specify which lanes to use and when.