Speed adaptation reason for major pet peeve

One of the more frequent “pet peeves” that readers recently sent me was about drivers entering a highway in front of another vehicle but not getting up to speed quickly, causing the other driver to brake. There’s a reason for this -“speed adaptation.”

Tom Vanderbilt, in his book “Traffic -?Why We Drive the Way We Do,” explains that the longer we drive at high speeds, the harder it is for us to slow down. The opposite is also true – when we first enter a main highway, we tend not to get up to speed as quickly as other traffic is moving because we are just beginning our trip or just entering a highway from a rural road where our speed has been much slower and we “feel” that we are going faster than we actually are. We don’t realize the vehicle that we pulled in front of is closing on us faster than we think, and if we force him/her to brake or slow down, it is irritating to that driver and becomes one of his/her pet peeves.

This phenomenon also holds when leaving a 30 mph village speed zone where the speed limit changes to 55 mph – it may take a vehicle a mile or more to get up to the speed limit because after going 30 for a period of time, even 45 mph “feels” like 55 or 60.

Have you noticed how fast traffic moves when entering our Franklin County villages, where the posted speed limit is 30 mph? Speed measurements show the speed averages in the 40s as vehicles enter our villages. Again, speed adaptation comes into play. When we have been traveling on 55 mph highways and are told to slow to 30 mph as we enter a village, 40 or 45 mph “seems” more like 30 because we have been traveling at 55 or 60 for some period of time. We are fooled into thinking we are going more like 30 when in reality we are going over 40 mph.

In essence, we underestimate our speed when asked to slow down and overestimate our speed when asked to speed up.

So now that we have identified a reason for a pet peeve, how do we correct for it? We can use pilots for a good example. They rely on their instruments rather than on what it feels like, and for good reason. A pilot’s instruments tell him whether the aircraft is turning, climbing, descending, air and ground speed, and much other information necessary for safe flying. What drivers should do is similar -?look at the speedometer. Don’t rely on what speed it “feels like.” You may be going much faster than what you think, or you may be going too slow for some conditions, such as a merge onto an expressway. It is also important to know the change in the posted speed zone you are leaving and the one you are entering, or perhaps the suggested exit ramp speed as posted on a warning sign as you exit an expressway.

Vanderbilt states that the reason we have speedometers, and why you should pay attention to yours, is that drivers often do not have a clue about how fast they’re going – even when they think they do. A New Zealand study measured the speed of drivers as they passed children playing with a ball and waiting to cross the street. When questioned, drivers stated they were going at least 20 kilometers per hour (12 mph) slower than they really were. They thought they were doing 18 to 25 mph when they were really doing 31 to 37 mph. Point made! The speedometer is accurate – our senses are not.


For more articles on Vehicle and Traffic Law and traffic safety, visit the Traffic Safety Board’s website at www.franklincony.org. “Like” us on Facebook as well.