The Non Contested Pass
A non contested pass is simply a pass where you're happy, for whatever reason, to let an overtaking driver go past with the least hindrance to them as possible. Your reasons may be that you don't want to risk an incident due to an overtaking battle, the overtaking driver may be known to you as a notorious accident causer, or you may be being lapped - in which case race etiquette requires you to do what you can to expedite a clean quick safe pass for the lapping driver. Whatever the reason, there may be times when you want to let someone past.
To let someone past uncontested, drive against one side of the track and maintain that position until they’ve passed. You need to use clear body language here. Moving from side to side trying to stay off the racing line, for the sake of the passing car, is the worse thing you can do. What’s important is not weather you’re on the racing line or not, but whether you’re driving a predictable line. Pick a side of the road to move to, usually the one you’re nearest to at the time, then religiously stay against that side until the car has passed. You might even try slowing a little to expedite the pass, as sometimes a quick pass can benefit you as much as it does the passer. But don’t slow down too abruptly of course.
In GPL during the race, if you're being lapped by another car you'll be shown blue flags by the marshals. These are advisory flags to let you know your about to be lapped and you're expected to do the gentlemanly thing and move out of the way.
In GPL, you may not always see all the cars behind you in your mirrors at a particular time. There may be several unseen cars close by around your tail. You may only ever see whichever one happens to be in your mirror's field of vision at the moment. This has special significance when you're being passed - with or without blue flags being waved.
If you're being lapped, perhaps with blue flags but whenever, be aware there could be any number of lapping cars right on your gearbox even though you don't see them. What can happen is this ... You see a car coming up in your mirrors, maybe you also see blue flags, you think " there's a car lapping me I'll move over to let him pass", you move to one side of the road and let him through, you then move back onto the racing line and BAM, you've hit someone. It turns out there was more than one car lapping you. When you moved over to let the first one through the others tried to go through too, as you'd expect. But while you were on the other side of the road, they were out of you mirrors, you simply never got to see them.
This can really take you by surprise, and them too. All you can do here is be as careful as possible, look around if you're able too, try to shy a glimpse, listen for more engine sounds, toggle the arcade view for a moment. They can help by trying to show themselves in your mirrors before going through. Be aware that just because you see one car go past that may not be the end of them. Whether after a blue flag or whenever, as the same limitations always apply.
The drivers doing the lapping / passing should also bear in mind these limitations. You ( passing drivers ) be aware that the car you're lapping may have absolutely no knowledge of your presence what-so-ever. Be careful. You should always try to show yourself in the mirrors of an ahead car before trying a pass.
The Contested Pass
The contested pass, or the pass done in anger, whatever you want to call it, is arguably one of the most difficult things to do cleanly without incident in GPL. Battling for position, passing and counter passing, wheel to wheel racing, is also the most fun thing to do.
The problem with close racing of any sort, contested passing included, is largely one of what each driver in the situation can see of the other. Most people I've raced with are fair and don't mean to cause accidents. Most aren't reckless. Its just that there's a lot of guessing going on about exactly where and how close you are to another driver. The GPL range of vision is much less than real life. There are huge blind spots to contend with. In fact the restricted visual range in GPL is so much a factor in close racing situations it warrants a detailed discussion in itself. The contested pass then is all about what you can and can't see.