How long are dashes on highway

So every time a car passes a new dashed line, the car has traveled 40 feet. But in this study, people consistently judged the lines and the empty spaces to be the same size, claiming that both were two feet. He acknowledges that the study will come as no surprise to transportation engineers, some of whom his team consulted with during the study. At each university, he and his colleagues measured lines on a variety of roads in the area.

Over those years, the federal guideline for line size has shrunk from 15 feet to 10 feet. Wherever the researchers went, they found all lines to be close to the federal guidelines of the time. In Arizona in , for instance, some lines were 16 feet long instead of the expected But even back then -- when the federal guideline was 15 feet -- people still thought of lines as measuring only two feet.

One possible explanation: as we drive, we look out far ahead the car for safety reasons, so the only lines we really see are faraway lines that look small. Rather, the first line we can comfortably look at while driving safely is some feet ahead -- the fourth line ahead on the road. Scientists have demonstrated this phenomenon in a number of contexts. In a study published in Psychological Science , for example, researchers found that people tend to perceive their dominant hand as staying relatively the same size even when its magnified.

Rather, the first line we can comfortably look at while driving safely is some feet ahead — the fourth line ahead on the road. So perhaps we think that all lines are as small in reality as that one faraway line appears to be. These line misperceptions have real implications for traffic safety. The empty spaces between each line measure 30 feet. So every time a car passes a new dashed line, it has traveled 40 feet. But in this study, people consistently judged the lines and the empty spaces to be the same size — 2 feet.

This means drivers are covering more ground than they perceive, and are thus underestimating their speed. I always thought the stripes were about eight feet in length. Too dangerous to get out and measure one. This was the safest way to ascertain the exact length. Or indeed any variation discussed in the article.

In that picture the lines are slightly longer than the gaps, whereas the gaps are supposed to be 3 times longer than the lines. So the road shown must be super safe according to their conclusions.

I agree with the researchers that anyone who thinks the lines are 2 feet long need to get their head read. My experience has taught me that a large majority of people have very poor skills when it comes to estimating anything involving motion— speed, distance, closure rate, etc.

The History Guy posted a YouTube video on the history of lane markers. He addresses some of the issues here but goes into much more detail about how they came to be and how they were standardized. APS regularly opens certain online articles for discussion on our website. Effective February , you must be a logged-in APS member to post comments. By posting a comment, you agree to our Community Guidelines and the display of your profile information, including your name and affiliation.

But even back then — when the federal guideline was 15 feet — people still thought of lines as measuring only two feet. One possible explanation: as we drive, we look out far ahead the car for safety reasons, so the only lines we really see are faraway lines that look small. Rather, the first line we can comfortably look at while driving safely is some feet ahead — the fourth line ahead on the road.

So perhaps we think that all lines are as small in reality as that one faraway line appears to be. Engineers design roads, buildings, and public spaces using Euclidian geometry — the system of lines and angles first described by the ancient Greek mathematician Euclid.

But this study and previous ones suggest that our brains perceive objects in a non-Euclidian way. In any case, the study is useful in quantifying what most engineers, and readers of Traffic , already know. Shaffer, meanwhile, carries on. In the future, Shaffer will examine how people perceive the size of lines that are oriented at different angles — as if seen by a driver approaching a bend in a road — and how our perceptions affect our ability to judge the steepness of hills.

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