Why do French people drive so fast?

Even though their roads are far narrower than in the US, French drivers love to drive fast, never slowing down to pass incoming traffic, bikers and unfortunately pedestrians. 

Granted, their cars are, on the average, much smaller, but if the road sign indicated a 50 miles per hour speed limit, they will not proceed below that speed, regardless of the circumstances. If in tight urban zones, it shows an 18 mile per hour sign, drivers conveniently read it as 30 miles per hour.

Driving fast seem to be an art form that, I must admit, is quite contagious because I too, wasn’t immune from that insane mania. Walking in the street is no more pleasant (diesel fumes, noise) than it is unsafe and we could never walk as much as we do in Park City if we had to live in Morzine and its surroundings. 

Short of widening the roads and creating sidewalks wide enough to be deserving of that name (a totally impossible task, since there’s no more room for it), people should avoid walking if they value their lungs and their lives. 

Maybe a possible solution lay in creating elevated or underground roads or limit access to pedestrians and cyclists only?