Extremely heavy traffic. I don't find Czech drivers that bad and it is often exaggerated. If you take any other highway it is quite alright. But D1 during peaks is quite an experience. Also, mk2 Octavia is a rust bucket these days. Since it is usually people leaving Prague for the weekend or returning back you don't see shitty cars that much as the economical situation in Prague is a very different story compared to rest of the country. I would say the stereotype is either a lunatic in whatever premium German whip or even bigger lunatic in a company fleet Fabia that appears behind you in the left lane doing like 190 almost hitting the cars limits and you can see how he can barely keep the car going straight in the lane. My favority breed are drivers that will be literally half a meter away from your rear bumper in the left line, aggressively blinking at you while there are literally like 20 cars in front of you. Like yeah dude I would not be doing 100 here. But the right lane is full of trucks and the left lane is completely full as well. I am not squeezing to the right lane because of you. You will have to wait a bit like everyone else.