Operating Within Laned Roadways
Vehicle Code 21658 brings up the way traffic must operate within lanes. Lanes are the painted columns that designate the areas of opposing traffic as well as, within a flow of traffic, where vehicles may travel next to one another.
If a roadway has been divided into two or more clearly marked lanes within traffic moving in one direction, vehicles must be driven reasonably within a single lane. This means that drivers must be aware of their vehicle and be careful to not glide over into other lanes without lawfully signaling. Switching lanes is allowed only if the movement can be made with reasonable safety and the use of a signal.
On certain highways, signs will designate whether slow-moving traffic should use a certain lane. Often, the signs will require slow-moving traffic to use the lanes toward the right side of the road where vehicles enter and exit the roadway. When entering and exiting a highway, vehicles must adjust their speed and often slow down to exit or slowly speed up to join the flow of traffic upon entering. Having the right lane designated for these changes, as well as those traveling relatively slower than the rest of traffic, allows other drivers to maintain higher speeds in the left lanes.
Drivers are responsible for knowing where they are on the road and driving respectfully within their lanes. Doing so helps drivers avoid collision with other drivers in nearby lanes as well as those in opposing traffic.