The occasional car-rattling jolt motorists are experiencing these days is a reminder that both spring — and pothole season — are here.However, thanks to a relatively consistent cold winter without the severe freeze-thaw cycle that creates wheel-busting potholes when water slips into cracks, freezes and expands, officials in the Corridor said damage to streets this year is pretty average.“I would say maybe above average to average,” said Brock Holub, Iowa City’s superintendent of Streets and Traffic Engineering.