While there actually may be signs posted in some locations, the prevailing state law in almost every state I'm aware of is keep right - except to pass.
regulatory
Slow traffic keep right sign
Slow traffic keep right sign
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Such signs often have the phrase "Keep Right Except to Pass" or "Slower Traffic Keep Right." Some places, like New York and Washington state add the words "State Law" to some of their signs.
Driving in the proper lane. In the United States this means driving in the lane that is on the right (---->) side of the road from the driver's perspective.
Slow traffic keep right sign
When you are in a country that drives on the right, then generally you should drive in the right lane; the left lane is for passing. When you are in a country that drives on the left, then generally you should drive in the left lane; the right hand lane is for passing only.
you should safely change to the right lane
true
the right lane
In Australia, where there are two parallel lanes for vehicles traveling in the same direction, the right hand lane is referred to as the "outside lane" and the left hand lane, closest to the curb, is the "inside lane".