SR2-38 track is 3mm wider than the SR2 track and Hot Wheels orange track, allowing for wider cars to race. It was originally designed for The Skyway's Short Circuit track. If Hot Wheels was going to start over and make a new track, my guess is that it would be closer to this lane width.
SR2-38 is compatible with SR3-38 but has solid walls instead of the guardrail look.
