The St. Louis Post Dispatch reported a couple of weeks ago about the new variable speed limit signs that have been installed along the 30 or so miles of Interstate 270, which is the main beltway surrounding the metropolitan area. The Missouri Department of Transportation wasted almost a million dollars installing these signs which are both ineffective and illegal.
The Federal Highway Traffic Safety Administration (which is, in itself, a monstrous waste of taxpayer money) issues a document called the Manual of Uniform Traffic Control Devices and requires all states to adopt this manual into law as a prerequisite to receiving federal highway funds (also known as extortion). This means that the MUTCD is federal and state law and is applicable to every mile of public road in the United States. It clearly outlines two criteria for speed limit signs: 1) an engineering study must be performed and documented for every single sign that is erected, and 2) the numeric value that appears on the sign must represent the 85th percentile speed (as measured in the absence of any speed limit) of naturally flowing traffic, rounded up to the nearest 5-mile increment.
You only have to drive I-270 for 10 or 15 minutes to discover that the vast majority of motorists are traveling at 70-75mph. But do these variable speed limit signs reflect that reality, and comply with the law? No. As the Post story indicated, MODOT has set the signs at 60mph, and will adjust them as low as 40mph when warranted by conditions. Do they really believe that anyone is going to drive 40mph on a four-lane interstate highway?
Imposing an artificially low speed limit results in unsafe driving conditions as some people will obey it and others won’t, which creates a dangerous speed differential within the flow of traffic. And studies have shown that it is not speed alone that causes accidents, it is dramatic differences in the speeds of vehicles sharing the same road that causes accidents. It is much safer to allow the drivers to choose their own speed based on their perceptions of the current driving conditions. In other words, no speed limit at all is safer than having a speed limit that can change at any given moment.
This is also a perfect example of an analog law that I wrote about a few days ago. Not only is there literally someone sitting there with their hand upon the dial, adjusting the law right before your very eyes, but there is an unimaginably costly infrastructure necessary to implement the law and provide for its enforcement.
The Post described this as an experiment. Well, it’s an experiment that costs too much, is in violation of the law, and is potentially unsafe for St. Louis area drivers. It’s an experiment we can live without.