Rants
The Big Speed Limit Lie
If you've driven on interstate highways in the US, you've probabably heard the phrase "double nickel". This is slang for 55 miles per hour, a limit on highway speed imposed by the federal government back in the 70's as a knee-jerk reaction to the 1973 gasoline shortage.
In order to ensure that states complied with the 55mph ruling, the federal government threatened to withold billions of dollars in highway funding from states that failed to show compliance. This was a double-dipper for the states. If they gave tickets, they got to keep their highway funding, and also enjoyed millions more in traffic ticket revenue.
Did someone say safety?
Before we try to apply safety to the 55mph limit, we need to understand how speed limits are set. Basically a new road is left unmarked, with no posted limit. Over the next few days, traffic engineers monitor the flow of traffic. They ignore the very fastest and very slowest of the speeds, and take the speed that 85 percent of the traffic travels at. This is called the 85th percentile speed.
Lets say, for example, the 85th percentile speed on a given road is 62mph. A traffic engineer would probably set the speed limit at around 60mph. This would mean only the very fastest of drivers (probably less than 5%) would be ticketed, which makes perfect sense. Now, let's take our road and reduce the speed limit to 45mph. What happens? Do the drivers slow down? No. A study several years ago sponsored by the Federal Highway Administration shows that regardless of the posted limit, traffic will flow at the 85th percentile speed. So since people don't slow down merely because the sign says to, more people are considered to be "speeding". Does the lower posted limit make the road safer? Of course not, since no one obeys it. Furthermore, even if the limit was obeyed, it would not have any noticeable effect on safety. Artificially lowering speeds below the 85th percentile does not increase safety. It just increases travel time and drivers spend more time on the road. This begs the question, how many accidents are caused by drivers falling asleep behind the wheel a few miles from their homes?
What if we took our road and raised the limit to 70mph. Would everyone suddenly stomp on the accelerator to take advantage of the extra 10mph? Most people would say "yes". The truth? According to the FHA study, a change in the speed limit, whether up or down, results in an average speed change of less than 1.5mph (yes, that's one and one half miles per hour). Don't believe it? Look at it this way: What if we raised the limit on our road to 150mph? Do you really think people are going to try to go 150mph?? Some might, probably the 5% we'd want to ticket anyway. It sounds logical that people would tend to push the posted speed, but remember, we're living in a world where the speed limits are set artificially low already, usually by around 15mph. If you raise the limit by 10mph, you are still below the 85th percentile speed.
Lowering speed limits below the 85th percentile does not make roads safer. It just increases the number of violators, and thus, the amount of revenue that can be collected from honest citizens who aren't really doing anything dangerous. Still think this is a democracy?
But I've always hear that "speed kills"
Speed alone does not kill. A car travelling down the road is more than just a math equation. A car has a driver who is constantly making decisions based on the road conditions, traffic, and a multitude of other factors. The part of speed that makes speed dangerous isn't the speed itself, it's the speed differential, that is, the difference in speed between vehicles on a given piece of roadway. Numerous studies show that traffic accidents increase as speed differential increases. The best way to picture this is to imagine two roads. On road "A", the posted speed is set at the 85th percentile, which means almost all of the vehicles are travelling at around the same speed. This could be 45mph or this could be 75mph. It doesn't matter. Now for our second road, "B". This road is posted 15mph below the 85th percentile. Here the speed differential is much larger. You have people driving at the 85th percentile speed who are now considered "speeders". You have people who are paranoid about driving at a comfortable speed for fear of being ticketed. You have people slamming on their brakes because they see a suspicious car parked in the median. And you have people jumping from lane to lane to lane to try to get around all the ambiguously driven vehicles. Does this sound safe? It isn't, but it's what we now have to live with.
But isn't 55 history?
Recently, the federal government lifted it's 55mph rule. Does this mean we're out of the woods? Not exactly. Just as it's difficult for a crack addict to give up his habit, it's also been difficult for many states to give up their cash cows. There are many highways still crippled by the double nickel. Many of these highways were designed for 70mph speeds back in the 1970s. This was before antilock brakes. Before radial tires. Before all the recent aerodynamic improvements. Before air bags and 3-point seat belts. It can be said that roads are more congested now than they were then, but this isn't true everywhere. There are still empty roads out there that a traffic engineer would set at 75mph that are double nickeled. Many come with a state trooper equipped with a radar gun. Is he making the road safer, or is he just collecting money?
What about the insurance companies? They say that lower speed limits save lives. The real question is, how would they know? Since we know that changing the posted limit doesn't effect speed, what are their statistics based on? The answer is that it doesn't matter. Rule number one for doing research is to ignore statistics from sources with a vested interest in the results. This makes any findings by insurance companies tainted. How do lower speed limits translate into money for insurance companies? It's simple. Insurance companies already know that the double nickel doesn't save lives. They also know that the limit is largely ignored. Regardless of these facts, most insurance companies consider one's driving record when calculating premiums, and speeding is something they love to charge for. Think about it. You have something you're allowed to raise rates for that doesn't neccessarily mean the driver is a high risk. In fact, most speeding tickets are given to drivers travelling at or near the 85th percentile speed! The speed that traffic engineers have determined to be a safe speed.
Unfortulately, it is unlikely that things will ever change. It's too easy of a sell from a "safety" standpoint that low speed limits are good. A vast majority of the public is totally uneducated when it comes to this topic, and most of them are more concerned with getting their kids to soccer practice on time than they are with who is fleecing them out of their rights. It's a shame that we bark about safety when drivers ed doesn't teach things like hands-on skid recovery, but parallel parking is drilled into students' heads. We're creating an entire generation of non-drivers who are put in front of speed limit signs that don't make any sense. How can we expect teenagers to obey the rules of the road when the rules we give them are based on nonsense?
