If you know what you're doing with your config files and roads you can quite literally have traffic do whatever you want it to. On a route I am currently working on I have traffic that runs on a 3 lane motorway with each lane going at a different speed, the ability for vehicles to 'randomly' change lanes and it works within the ATLS system (though that has been problematic). Most things are achievable in the game but they sometimes take effort and a bit of artistic license to accomplish.