Deliberate mistake: When the Tennysons drive towards the city's power plant, Grandpa Max is using the left side of the highway instead of the right. Even with a looming nuclear accident, correct traffic habits do play a role, especially on such a narrow highway. Who knows whether one might drive down the road in a hurry and you approach him on his side of the highway?
Other mistake: When the Tennysons drive towards the city's power plant, Grandpa Max is using the left side of the highway. Curious, since you drive on the right in the USA - regardless of the looming nuclear accident there was no reason to invite a crash like that.
