Generally speaking, you should only pass other vehicles on the left when you're driving. Passing on the right is often unexpected and therefore more dangerous than passing on the left.
That said, many people do pass on the right in their cars, on their motorcycles and on their bicycles. Examples include when a car passes traffic at a red light in the right-turn lane and when a cyclist goes by in a bike lane.
Even when passing on the right is legal, it can put you at risk. The problem is that a driver in the left-hand lane may:
- Begin to drift over to the right without realizing it.
- Not recognize that the other lane is there at all.
- Make a sudden turn to go down a side street or to pull into a driveway on the right side.
- Make that turn without signaling and/or without looking to see if the way is clear.
- Open a gap in the stopped traffic so that an oncoming vehicle can turn left; this other vehicle may be invisible to someone in the right lane, but they can suddenly cut right across that lane.
- Open up the passenger-side door of the car to let a passenger get out.
All of these actions can cause an accident. In some cases, the vehicle on the right may be breaking the law, but the truth is that even legal right-lane usage can lead to accidents. You have to stay vigilant and understand the risks that you face.
If you do get injured, it's also important for you to understand all of the legal options you have.