Idaho's primary keep-right rules are found in Idaho Code §§49-630 and 49-655.
A vehicle traveling at less than the normal speed of traffic under the existing conditions generally must be driven in the right-hand lane available for traffic, or as close as practicable to the right-hand curb or edge of the highway.
This slower-traffic rule does not apply when the driver is overtaking and passing another vehicle traveling in the same direction or when preparing for a lawful left turn at an intersection or into a private road or driveway.
Idaho also prohibits driving so slowly that normal and reasonable traffic is impeded unless the reduced speed is necessary for safe operation or required by law.
On controlled-access highways, a driver may not remain in the extreme left-hand lane for a period of time that impedes the flow of other traffic traveling at a lawful rate of speed.
Idaho therefore combines the traditional slower-traffic keep-right rule with a more direct restriction against blocking lawful traffic from the far-left lane on controlled-access highways.
Exceptions
- Overtaking and passing another vehicle traveling in the same direction.
- Preparing for a lawful left turn at an intersection or into a private road or driveway.
- Avoiding an obstruction when moving left is necessary and safe.
- Traveling on a roadway divided into three marked lanes where another lane position is permitted.
- Traveling on a roadway designated for one-way traffic.
- Driving at a reduced speed when necessary for safe operation or required by law.
Penalties
Violations of Idaho's keep-right and minimum-speed rules may result in a traffic citation.
Idaho's traffic-law schedule assigns three points to a violation of §49-630, Drive on Right Side of Roadway.
The exact fine and total amount due can depend on the violation and court assessments, so drivers should verify the amount shown on the citation or with the court handling the case.
Official Source
Idaho Code §§49-630 and 49-655 - Keep Right and Minimum Speed Rules
Last verified: October 11, 2026