In 1974 Congress passed the National Maximum Speed Law (NMSL) establishing 55 mph maximum speed limits across the United States in an effort to reduce fuel consumption (that 1973 Oil Embargo done spooked 'em good) and reduce highway deaths (as most modern safety features, from airbags to tempered glass, were not yet in place). Some people argued that the law worked, others argued that it failed, and pretty much everyone agreed that driving long distances on empty country roads or Interstate highways at 55 mph sucked a whole bunch. Furthermore, oil shocks and 1950s Deathmobiles were a thing of the past, so in 1987 the law changed to permit 65 mph limits; in 1995 it was repealed altogether. Since that time, speed limits across the country have been creeping upward. Texas – really, who else? – and Utah currently lead the nation with an 80 mph maximum. Don't worry, though. Texas about to raise it to 85, which would be the highest posted speed limit in the world.
In 2010, the last full year for which data are available, total motor vehicle fatalities in the U.S. were the lowest since 1949. That's incredible if you stop to think about it. We drive a ridiculous amount as a nation and at increasing speeds, yet fatalities are declining sharply. This is evidence that today's new cars, with their dozen airbags, ABS, safety cages, crumple zones, and countless electronic safety features, are clearly capable of handling 65/70 in relative safety (NB: car accidents are still a leading cause of death for every age group under 55).
That said, 80 and 85 mph limits seem to be tempting fate at the point at which the average driver's skills and the physical limits of many of the cars on the road are strained. I'm going to start from the assumption, possibly overweighting my own preferences and experience, that most of us and our vehicles feel comfortable cruising between 70 and 75 mph on the highway in good weather. Since speed limits are neither followed nor enforced strictly, let us assume that posted limits of 80/85 mean that actual traffic will move anywhere between 85 and 90+ mph.
As a parent, child, or both, most of you have said or heard the phrase, "It's not you I'm worried about – it's all of the other drivers" at some point in your life (Is there anything we agree upon so completely in this country as that Other People are terrible drivers?) Simply put, 90 mph is really fast. Probably much too fast for most drivers to do safely. Cars handle much differently at that kind of speed and the time available to react to the road declines precipitously.
The real issue, though, is…well, look around you on the road. Maybe even look at your own car. Lots of us are driving what could charitably be called shitboxes. Unlike motor vehicle fatalities, the average age of vehicles on the road in the U.S. is at a record high of 11.2 years. Remember, that's an average in a year in which new vehicles sales increased sharply. We're talking about a lot of 15+ year old vehicles out there. And I'm sorry to say that your 1990s minivan, compact car, or family sedan is not really in any kind of condition to drive 90 mph. Hop in your 1994 Taurus or 1997 Chevy Cavalier, try going that fast, and tell me that you did not begin to lose faith in the structural integrity of your vehicle (and the validity of your will) beyond 75 mph. I'll wait.
Even with new-ish cars, the safety margins and specifications are for a new vehicle. Even regular age and wear dramatically reduce the car's capabilities in a short time. You might think that your 2008 car is still fairly new, but the shocks are softer, the steering is looser, and the brakes have a lot more play in them compared to when you drove it off the lot. Since most people skimp on or completely ignore regular maintenance on their cars, this is a big issue. But the biggest issue is your tires. Most compact and midsize cars, even brand new ones, have P, Q, or R speed rated tires. This means the design limit of the tire is between 95-105 mph. Consider how many cars are driving around on worn-out tires that should have been replaced years ago. Now consider those same cars being pushed to and beyond their speed ratings. Yeah.
I'm not so comfortable with Other Drivers doing 90. If everyone drove a brand new Volvo and had good driving skills, jacked up speed limits would be irrelevant. Here in the real world, that ding-dong in the 1991 Plymouth Duster (with more Bond-O than metal in the body at this point) going 90 on bald Chinese summer tires that he bought for $19.99 at Tire Barge's 2003 President's Day Blowout sale is probably going to kill someone. A lot of the vehicles on the road are not even safe at 70 or 75, and the danger increases exponentially at higher speeds. Since we seem to be so eager to follow the example of the Red States these days, I'm not looking forward to what another decade of Speed Limit Creep is going to bring.