We've been saying for years that the most dangerous thing in Mexico is not the cartel assassins, but rather everyday drivers. (For instance, today there was a double firefighter funeral - the first we're aware of in all the years we've been here. Of course, they didn't die in the line of duty [everything here is made of stone], but in a spectacular one-car accident that killed both men and the pregnant wife of one them.)
Not to let Mexican drivers off the hook (they're truly, truly insane), but a big part of the problem are the highways here. If you took a bunch of reasonably intelligent, well-intentioned people who had never seen anything but dirt roads and asked them to design a highway system, you'd probably come up with something similar to the actual roads circling this city. If, on the other hand, you asked those same people to avail themselves of the nearly 100 years of human experience building highways around world, they would realize that giving drivers less than 50 meters in which to merge onto a three-lane highway is a terrible idea. Or that entering from the right and exiting from the left is really hard to do in less than 100 meters when you have to cross four lanes of traffic (occupied by Mexicans). Or that placing an offramp before an onramp makes sense, while doing the opposite inevitably leads to fatalities. Or that speedbumps on a highway are never, ever, ever, under any circumstances, ever a good idea. Even less so if you paint them the same color as the rest of the road.
One random example - well, not exactly random since it's almost killed us twice in 14 days - is the road to get into Juriquilla. After driving several miles on 5 de Febrero/Rt 57 (the deadliest road in Querétaro), you get off onto a long, straight, three-lane road where, since it's Mexico and the road is long and straight, you can expect to reach speeds in excess of 60mph. And then you take the exit to Juriquilla:
Why yes, that is a stone wall, thank you for noticing. And, no, no one involved in building the road seems to have thought this was a bad idea! Despite having acres and acres of empty space in which to construct a graceful, gently-arced exit road, this turn is literally tighter than 90 degrees (see the link above - the photo is the view facing west). Of course, if you're going too fast and didn't realize that there was a 100-degree turn up ahead (because there's no sign explaining this, or, if it's nighttime, because there are no lights), don't worry! The overpass's stone wall will slow you right down.
As an added bonus, please note the pedestrian stairway in the middle. Pedestrians can use this to cross safely over the six-lanes of traffic, only to be deposited right on the sharpest part of the exit's curve, where they will either be crushed between an out-of-control vehicle and the stone wall, or plastered in the middle of the road by a driver lucky enough to have made the turn in time. Of course, such accidents are extremely rare because most pedestrians would simply sprint across the six-lane highway rather than take the pedestrian bridge.