Ok just so people aren't confused, because i feel there's confusion, here's the text for Chase Combat, SR4A pg. 169:
Chase combat is radically different from ordinary tactical combat.
Because everyone is moving around quickly, it’s nearly impossible and
practically pointless to keep track of everyone’s position. Instead, chase
combat is handled in abstract terms, where each driver tries to maneuver
his vehicle to gain an advantage over his opponent(s).
So the thing is i'll just SCRAP the diagram because that makes you guys wanna think too linearly and geometrically. Distances and positions are totally abstracted so create whatever layout you want in your mind, but just remember that all that matters is if the engagement range is short, medium, long, or extreme and the only way to change these is by winning a set-up test. This gets rid of the confusion when engagement range is changed between only two vehicles because if you're thinking about positions, this should logically change the engagement range between all 3 vehicles. But we're ABSTRACTING it because it's assumed you're change actual distances constantly and fluidly and it's not all the time based on where you wanna go but also what other cars, obstacles, or turns on the road force you to do. So rather than get bogged down in details, it's all just boiled down to engagement ranges. Don't think linearly....and I apologizing for putting up that linear diagram, i was just trying to think of some way to express the information of engagement range in play by post...(this is my first PbP vehicle combat...but i've done it table top several times)....but it was a poor choice of representation. Now i'll just say what the range is between all parties involved.
So please don't complain when logic seems bent a bit when cars change their engagement range. Just imagine the road as a rather 2dimensional playing field rather than a linear playing field and i'm sure you could resolve whatever issues with logic that you may be having. The only "logic" i'll use is the idea that Rover is in the lead, and currently Zach and Driver are together. Now it'll get weird if Driver passes ahead of Zach and changes to Short range with Rover, but Zach somehow is still Long Range from Rover, but still Short Range from Driver. It gets all screwy logically.....and multiple opponent Chase Combat is weird like that...and best designed for just two sides. But since Zach really wanted to have movement independence and not always be close to the Rover, we'll just do it like this and ignore that logical fallacy. We can just fix it like this:
We won't really care what distance Zach is to Rover, but if he ever cares about his distance to the Rover...i'll just make him do a Vehicle Test and he can get to whatever range he wants to it....and the difficulty will be how much the change in range is.