I'm wondering if a mod could make the traffic system less demanding, since it sucks not being able to use it most of the time. The traffic really makes some maps come alive so it would be nice to be able to use it. I'm not sure if this would work but maybe a mod to unload vehicles that aren't in the players sight, to save on resources? Or maybe an option to enable traffic and set/limit how many ai vehicles spawn before loading into a map?
Options > Gameplay and you can set the amount of vehicles Traffic spawns. By default it's set on an automatic, based on how many cores your CPU has. Aside that, it depends from your hardware. If your CPU can't keep up simulating 2-3 vehicles, your CPU is too slow to use traffic.
"unload vehicles that aren't in the players sight, to save on resources?" That's how it works to begin with. "an option to enable traffic and set/limit how many ai vehicles spawn before loading into a map?" You can already set that.
I made 4 low node count cars in Automation. I don't know if anyone has made a specific mod for something like that. Should I make these available on the site/mod repository? In most games traffic cars have less detail/simpler physics than player controlled cars. These vehicles only have few pieces of trim. Most if not all are AWD and have lots of low end torque to help reach their speed limit without doing a burnout. They aren't fun to drive but they are fun to swerve around/clip at highspeed. I don't think I gave any of them anything more than ABS.