It depends on the radius of the curve. The signs on sharp curves are generally posted to keep you under 0.25g. So, the 0.3g figure is not much higher than following the speeds posted on the signs exactly. Most people when driving will feel comfortable taking a corner at 0.4g to 0.5g. Most SUV's can generate 0.6g to 0.8g of cornering force. Automobiles generally can attain 0.7g to 0.9g, with the best sports cars capable of 1.0g or a little more on street tires. Thanks, I knew that .3g laterally was within the capability of most cars. But, I was looking for an example. I chose the "right turn around a corner" as an example of turn most people would recognize.
So, if we presume that we are turning right 90 degrees at an intersection, in a short radius turn (say, 3/4 of a turn of the wheel, not to lock), from right lane to right lane (not fair straying into the center or left lane). What speed would you need to generate a .3g lateral acceleration due to centrifugal force?
Not sure about the corner thing. But G force varies with the square of speed. So, taking one of the loop around freeway exit ramps with a posted speed of 25mph on the warning signs at 27mph would generate about 0.3g. If the sign says 20mph, take it at 22mph for about 0.3g.
Around here, most people do 30mph to 35mph around the ones marked 20mph and 35mph to 40mph around the ones marked 25mph. Generally that's in the 0.5g to 0.6g range.