What You Should Do When You See Black Cables on the Road

Alright—so here’s what happened. I was driving to pick up groceries. Not in a rush exactly, but not not in a rush either. And I go over these two black rubber cable things on the road. You’ve probably seen them too—just laying there across both lanes like someone forgot to clean up after some utility work. They make this little thunk-thunk under your tires, and that’s it. No flashing lights. No signs. Just there.

I see them around town sometimes. Never gave them a second thought until my passenger—my sister, who notices everything—goes, “What are those actually for?” And I froze. I’ve been driving for years. You’d think I’d know. I didn’t. Not even close. I was kind of embarrassed not gonna lie.

I said something dumb like “maybe… pressure sensors?” And then I did what I always do when something makes me feel clueless—I Googled it later in bed, still holding a spoon from the yogurt I never finished.

So, those cables? Let me tell y’all. They’re not random. They’re actually called pneumatic tubes, and they’re used for counting cars. Like—literally counting them.

Here’s how it works, and I’m not pretending I totally understood it on the first read: Every time a car drives over one of those tubes, it pushes a little burst of air through the line. That puff of air hits a counter device connected at the end—like, physically hits a sensor—which logs it as a car. Just… click. That’s one.

Now, if there’s just one tube? It’s probably just counting how many cars passed in a certain timeframe. Basic stuff. But when there are two? Spaced a few feet apart? They can actually measure how fast the car was going and what direction it was heading. In some cases, they can even guess the vehicle class. As in—was it a sedan, a truck, a motorcycle. Wild. All from a rubber hose.

And then the information goes somewhere. Like, actual people (transportation engineers? I assume someone with a clipboard?) use this data to make decisions about traffic patterns. Timing stoplights. Adding or removing turn lanes. Stuff that actually affects your morning commute even though you never think about how it gets decided.

I asked someone once—just out of curiosity—how they figure out where to add a new stop sign. And they told me something like, “Traffic volume and speed data over time.” Which I nodded at like I understood. I didn’t realize until now, this is how they get it. These tubes are basically the front-line workers of urban planning.

They’re not just about traffic volume either. If there’s a stretch of road where people are constantly speeding, the data from these tubes can help flag that. Maybe nothing happens. Or maybe the city installs speed bumps, or those digital signs that flash your speed at you and make you feel personally attacked.

And apparently, they also help with bus planning. I didn’t know this. But let’s say a bus route keeps getting delayed during rush hour—this kind of data can tell the city if it’s traffic or just bad timing. That’s how they decide whether to adjust schedules, add a lane, or change the route.

Even snowplow schedules, weirdly enough, can be influenced by this kind of traffic monitoring. Like, roads that don’t get much traffic might get de-prioritized in winter storm plans. I had no idea. I thought it was just bad luck that my street always gets cleared last.

What’s kind of amazing is how invisible all this is. You drive over a cable—doesn’t beep, doesn’t flash, doesn’t ask anything from you—and yet it’s collecting real-time data that shapes the infrastructure around you. It’s like the road’s keeping a logbook and you’re in it, whether you like it or not.

And yeah, sometimes it feels like cities make bad traffic choices anyway (ok, more than sometimes), but honestly, the data doesn’t lie. If anything, it’s the best argument for not just going with gut instinct. This little air tube knows how many people drove over it at 7:14 a.m. last Tuesday. Your memory doesn’t.

I’ve started noticing the cables more now. There’s one near the school where the traffic gets ridiculous every morning. Another by the mall. They’re not always there long—usually a few days, maybe a week—but they always show up before something changes. Like a warning sign that the city’s about to make a decision.

Those black cables are just doing their job. Quietly, which, honestly, is kind of refreshing.

Also? No, they’re not recording your license plate. Probably.