All states have laws that prohibit drivers from making unsafe lane changes. State laws generally require a driver on a road with marked lanes to operate the vehicle within a single lane and to move to another lane only at a time and in a manner that is safe.

This means a driver may not cross more than one lane of traffic at a time, must allow a safe distance between the driver’s vehicle and other vehicles, and must signal the lane change with a blinker, as required by law. The failure to do so may result in a ticket or citation for an unsafe lane change.

The penalty for making an unsafe lane change usually includes a fine and demerit points on your driver’s license or record.

As with many traffic violations, the officer issuing the citation and the prosecutor have significant discretion in determining whether there was a violation of a traffic law and whether the violation constitutes a certain offense, as defined by the state legislature in the traffic code or in a municipal ordinance.

This discretion to issue a ticket or citation and prosecute the charge against the driver is balanced by the discretion of the jury or judge in determining whether the prosecution met its burden of proof sufficient to convict the driver (for a criminal offense) or find the driver responsible (for a civil infraction, violation, or offense).

In Arizona, laws governing unsafe lane changes are outlined in Arizona Revised Statutes § 28-729, which mandates that drivers must remain within a single lane and only change lanes when it can be done safely. Drivers must not cross multiple lanes of traffic at once and must maintain a safe distance from other vehicles. Additionally, signaling the lane change with a turn signal is required by law. Failure to adhere to these rules can result in a citation for an unsafe lane change, which typically carries a fine and may add demerit points to the driver's license record. The discretion to issue a citation and prosecute the charge lies with the law enforcement officer and the prosecutor, respectively. However, the final determination of guilt or responsibility rests with the judge or jury, who must decide if the prosecution has met its burden of proof.