You exit the freeway and pray to catch the green light at the interchange so your journey continues in one smooth swoop.

But more often than not you'll catch a red light and slow to a complete stop as you wait your turn to move along. Same thing when you want to get on the freeway - you have to wait your turn.

These scenarios are played out every hour of every day across Perth - drivers killing times at interchanges ruled by traffic lights calibrated to regulate traffic.

But the new Mitchell Freeway extension in Perth's northern suburbs is aiming to tweak this by installing the very first roundabout controlled freeway on and off ramps ever seen in WA, keeping traffic flowing instead of bringing it to a halt.