California Vehicle Code 21658 makes lane straddling or unsafe lane changes illegal. Lane straddling is defined as drifting into a lane next to the lane a person is driving in, with their car “straddling” the line between the lanes. Violations of CVC 21658 are often used as a pretext for law enforcement to initiate a DUI stop.
Text of CVC 21658(a):
21658. Whenever any roadway has been divided into
two or more clearly marked lanes for traffic in one direction,
the following rules apply:
(a) A vehicle shall be driven as nearly as practical entirely
within a single lane and shall not be moved from the lane until
such movement can be made with reasonable safety.”
The full text of CVC 21658 can be found here: CVC 21658.
CVC 21658 applies to “Laned roadways,” or roadways that have two or more lanes in the same direction. This means that CVC 21658 does not apply if there is only one lane for each direction of travel, like a country two lane road.
The rule in CVC 21658 is that a person driving in one of these lanes must do so as nearly as practical to the center of their lane. Small, momentary deviations within a lane are allowed, so long as they do not create a hazard to other drivers.
Changing lanes safely:
CVC 21658 (a) creates a duty to change lanes only when it is safe to do so. This means a person driving on a divided road with two lanes in the the same direction should not cut off other motorists, or change lanes without using their turn signal. If a driver does either one of these, it would create an unnecessary hazard to other motorists and therefore violate the requirement to initiate such movement with “reasonable safety.”
Probable Cause for DUI cases:
Drivers on California’s roadways enjoy Constitutional protections against unreasonable interference from law enforcement. This means a person has the right to travel without fear of being stopped by police, and a reasonable expectation of privacy if they are not violating laws while traveling on roads in California.
If a driver does violate a vehicle code section, a law enforcement officer then has justification to stop the motorist. This type of temporary detention is called an “enforcement stop.” During an enforcement stop, police will approach the vehicle and ask the driver for their license and registration. If the officer smells alcohol, or can see objective signs of impairment on the driver, such as slurred speech, a DUI investigation will be commenced.
CVC 21658(a) Reference Links:
California Vehicle Code: The California Vehicle Code has thousands of sections and subsections, including CVC 21658(a).