Traffic Engineers are Tricky

Noise and Vibration (Shock and Awe)

What I’m about to reveal may cost me my career. But what gives me peace of mind, is I believe you guys are trustworthy — especially when it comes to traffic engineering secrets. I also believe you are reasonable. Granted, some feedback I receive is unreasonable, but I maintain that even reasonable people are capable of unreasonable feedback (usually the result of cheap coffee). So, if it saves time, please know I completely ignore unreasonable feedback (I’m talking to you, Carl).

One of the trickiest things traffic engineers ever invented are transverse rumble strips (TRS’s). You have all seen them (i.e., heard them). Through noise and vibration (i.e., shock and awe), they draw your attention to unexpected changes in roadway alignment or conditions requiring a speed reduction or a stop (like temporary road construction).

Transverse rumble strips are composed of very thick paint (melted plastic actually) to create the rumble effect — somewhat akin to lactose intolerance (future column idea). The thermoplastic “powder” is melted to 400 degrees and applied to the roadway surface to create tactile/audible feedback for pavement markings, crosswalks, stop bars, and of course, rumble strips. They last longer than standard paint and contain reflective beads to improve nighttime visibility.

Here’s the tricky part, transverse rumble strips may appear evenly spaced but in actuality are spaced closer and closer (and closer) to each other. In fact, the inter-rumble-strip (IRS) spacing decreases with each strip to the point that the last few strips are actually placed in front of the last few strips. This illusion tricks your brain into thinking you are accelerating when in reality your speed may be unchanged or even slowing. The sensation is so effective, some drivers are convinced rumble strips cause their car to speed up (only to be enlightened by their local automobile mechanic for approximately $85, not bad — if you find a better price, please let me know).

As always, please use this knowledge responsibly. Traffic engineering is both art and science. The answers are not always found in books (and I’m not just saying that because I can’t find my books).

Chet Skwarcan (traffic engineer, author, unique insights) with over 25 years of traffic engineering experience — online ideas available at TrafficEngineering.com/Services.

 

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