LAX APM platforms are designed for 4 car operation.

This train is very commonly used in airports in the US. SFO and DFW both run 2 car per train while SEA and LAS runs 3 cars per train as default configuration (they can add extra cars during peak time). I believe LAX will be the first to run 4 cars as standard configuration in North America.

The only 4 car default operation for Innovia APM that I'm aware of is Taipei Metro Brown line.