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Speed bars on the side of the road have become a new strategy employed by government officials determined to slow down highway speeders. And it’s working.

When your brain sees the bars flying by, it registers in your mind that you are going fast. Possibly too fast. So you slow down a little to compensate.

Daily Deception explains further:

The white bars are installed a certain distance apart, but when approaching an area where traffic should slow down, the bars are spaced closer together.

This gives drivers the illusion that they’re going faster than their actual speed. If drivers perceive the bars traveling by at 4 seconds apart and then they see them start whizzing by at 3 seconds apart, the theory is that they’ll assume their vehicle is speeding up, and they’ll slow down.

Reports say that drivers slow down by an average of five miles per hours when driving through the speed bars.