The passenger inside the car is in the reference frame of the car so he experiences centrifugal force

= \(\frac{mv^2}{r}\) acting on the car. So, to remain in circular path force should be larger as it is proportional to v^{2}. For an observer on the road side finds that the centripetal force \(\frac{mv^2}{r}\) acting on the car becomes inadequate with increases in v. Since again v^{2} ∝ r is insufficient so the car skids.