ESP is supposed to help correct situations where the car is turning, and begins to slip at either the front or rear: ESP brings the car back to the intended path by braking some wheels and reducing power.
Question: Does it work when the car is going in a straight line? Suppose two wheels go off the edge of the road onto grass or some other surface where the rolling resistance is higher than the road surface. The car will immediately pull off the road. Would ESP correct this by applying only the brakes on the wheels that are still on the road? Or does it require lateral g-loading as would be generated by going round a turn?