I don't know if smart is the right word and I very much doubt IQ is the correct measure, but you do need to evaluate dozens of factors quickly and continuously

I don't know if smart is the right word and I very much doubt IQ is the correct measure, but you do need to evaluate dozens of factors quickly and continuously while driving, always paying attention and updating your risk assessment. It's a mentally taxing exercise and many people can't do a remotely good enough job.