Transverse rumble strips, or bar markings, are installed on roads to alert drivers of hazards ahead, such as bends, intersections, or high pedestrian activity areas. But did you know that some rumble strips were designed for something else?

A part of Route 66 in New Mexico has an unusual set of rumble strips. They were designed to sound like the song “America the Beautiful” if you drive through it at precisely 45 miles per hour.

What Are Rumble Strips?

Rumble strips are grooves or indents installed in the pavements. It is designed to alert inattentive drivers through noise and vibrations transmitted by the wheels as they pass through it.

These strips are found on different parts of the road, with each having a different task from the other:

• Road Shoulder – These strips are longitudinal strips outside of the edge line. It is designed to alert drivers that they are leaving the roadway and going into the shoulder. Its goal is to reduce run-off-the-road crashes.
• Lane Edges – These one’s designed to separate the travel line from the road shoulder.
• Center Lines – These strips are installed to separate opposing traffic or undivided highways. Its goal is to reduce head-on and opposite-direction side-swipe crashes.
• Middle of the Lane – Strips that are placed across the travel line to alert drivers that they are approaching a change of roadway condition or a hazard, and its goal is to make the drivers reduce their speed.

In order for rumble strips to be effective, they should be able to create noise transmitted to the interior of the vehicle, and that the noise increase should be within the 6-15 decibel range. In recent studies, rumble strips have helped reduce lane departure crashes significantly. (Source: Minnesota Department of Transportation)

The New Mexico Musical Highway

In 2014, the New Mexico Department of Transportation partnered with the National Geographic Channel for a unique project. The partnership was to create rumble strips and encourage drivers to adhere to the speed limit. The rumble strips were installed on route 333, which is part of the old route 66 system. It is located between mile markers 4 and 5, near exit 170. (Source: Atlas Obscura)

The project was unusual because the rumble strips weren’t ordinary strips. They were engineered to sound like the song America the Beautiful. The song will only be heard if drivers pass through the strips at precisely 45 miles per hour.

The San Bar Construction Corporation engineers deduced that sounds and music notes were vibrations that resonated in the air. They had to compute the number of rumble strips and exact spacing to create the specific note to be heard as the driver passed the groups of stripes. Each strip is precisely 2.4 inches spaced from the other.

For example, to produce an E-note with a car, the arrangement of the rumble strips was to be spaced accordingly such that if the car goes at 45 miles per hour, it will hit precisely 330 strips. This would then produce the E-note. The engineers then broke down the song per note needed, designing the strips to play all the notes, completing the piece. (Source: Considerable)