For a PDX, there are strict rules on where and how you may pass other cars.

Passing is permitted only in designated areas. The passing zones will be detailed during the drivers meeting. 

Passing is ONLY allowed with a point-by. You may pass only in designated areas and only after receiving a pass signal from the driver being passed. The overtaking car passes off-line.

Watch your mirrors! If a train, or line, forms, behind you it is your responsibility to “clear your rear” by safely allowing cars behind you to pass.

When it becomes apparent someone wants to pass you, stay on line, give a clear, specific signal (a point of the index finger) and lift slightly off the throttle! Do not resume full acceleration until the car has passed.

As the passing driver, after receiving the passing signal, check your mirrors, pull off-line and accelerate smoothly past the car you are overtaking. Be sure to make a clean, complete pass and do not come back on line until you are well clear of the passed car.

The driver being overtaken must give a clear hand signal for each and every passing car.
Just because the car in front of you got the passing sign does not mean you got one. If in doubt, don’t pass.

If you did not get a pass signal, be patient, and do not tailgate. The driver ahead of you may be overwhelmed and riding their bumper won’t help.

If a passing signal is not given during that lap, pull into the pit lane the next time by, drive through slowly and wait at pit out for signal from the Pit Control worker so you re-enter the track in another position.

Do not attempt to pass at the end of a straight. Be sure you have the time and room before you attempt a pass. All passing must be completed before any corner. Never pass under a YELLOW flag.