What if the Road Could Tell Us What It’s Feeling?
The Revolutionary Technology That Will Change Everything
Imagine for a moment you’re driving on a dark, winding road late in the evening. You haven’t seen another car for miles in either direction. Then, as you’re approaching a hill, you get an alert on your phone warning you that there’s a road hazard ahead. You let off the gas and approach cautiously. As you crest the hill, you notice a large tree had fallen and is completely blocking the road. Had it not been for the warning, you may not have had enough time to stop before either hitting it as you crested the hill. Fortunately, you were notified in advance and approached cautiously enough to stop. Crisis averted.
On a busy roadway, it’s likely that other drivers will report obstacles like a fallen tree using applications like Waze. However, events that occurred very recently or on a roadway with low traffic volume may not be reported right away, if at all. If there are no other drivers to warn us of a hazard, how are we supposed to know?
While incidents like a tree in the road are somewhat common and rarely involve anything more than a mild inconvenience, we occasionally experience much more serious events. Just a day before this writing, a bridge collapsed in Pittsburgh along a section of road that sees a high volume of traffic. Fortunately, it seems there were only relatively minor injuries. However, had it occurred during the evening rush hour, the situation could have been much worse, as it’s common for outbound traffic to back up to a standstill along that section. I’ve spent plenty of time sitting in traffic at that very spot myself.
Such incidents seem to be occurring with greater frequency, but they don’t have to. With the right information, these disasters can be predicted and avoided. The circumstances that lead to these incidents often include warning signs that aren’t always visible upon normal observation. There are processes and procedures designed to catch any such conditions that may lead to failure, but these processes are typically expensive, difficult to perform, and often require expensive equipment. As a result, such assets are typically only inspected at pre-defined intervals. In the case of such failures, this often leads to regret — “If only we had noticed sooner.”
That’s not possible using existing methods. Even when using modern inspection equipment such as UAVs, you can only inspect something so often. It’s simply not feasible to inspect every road, bridge, and building every single day, every week, month, or even year. While the conditions leading to this bridge collapse appear to have been both visible and obvious, there are many cases where they aren’t.
We need a better approach. What if instead of inspecting the road, the road can tell us how it “feels”? No, you didn’t misread that. If you think that sounds a bit nuts, you’re likely not familiar with Fiber Optic Sensing.
What is Fiber Optic Sensing?
Fiber optic sensing uses the unique properties of light traveling through fiber optic cables to monitor the surrounding environment. In effect, one or more fiber optic cables act as “nerves,” providing anything they are installed in or on a variety of “senses,” including vibration, pressure, strain, temperature, and sound. These properties can be read continuously along the full length of the cable, up to many dozens of miles or more with current capabilities. This makes it possible to monitor hundreds and even thousands of miles of assets cost-effectively.
What can it sense?
Fiber optic sensing can detect various physical phenomena, including vibration, strain, temperature, and sound. By monitoring these phenomena individually or together, a substantial amount of information can be gathered about the environment surrounding an installed cable.
Vibration
Vibration is one component of what we think of as the sense of “touch.” Through vibration sensing, we can determine the presence and location of a car, a person walking, a rock rolling down a hillside, or someone climbing a fence or wall.
Strain
Strain sensing effectively permits sensing the configuration of the cable itself to derive information about the conditions where it’s installed. With strain sensing, it is possible to determine various physical properties of the cable, such as shape/bending, elongation, and twist. When attached to or embedded in a surface, this effectively conveys information about the physical nature of the surface, such as shape changes, movement, and orientation. This type of sensing is particularly useful in situations where a change in shape or configuration is noteworthy, such as structural members or landslide/slip monitoring.
Temperature
Temperature can be read along the full length of a fiber optic cable. This is particularly useful when monitoring linear assets such as pipelines, electrical cables, or roadways. An important feature is the ability to monitor differences in temperature along the cable. In the case of a high-pressure pipeline, one section with a dramatically different temperature may indicate a leak or other issue. In roadways, sensors may report road sections subject to freezing and icy conditions.
Sound
A fiber optic cable can serve as a continuous linear microphone. With this in mind, it’s possible to determine the location of a specific sound, listen to the sound at a specific location, and perhaps even follow a sound source as it moves along the length of the cable. This can be particularly useful for monitoring for specific sounds, such as the sound of a leaking pipeline or arcing of electrical wires.
Location
An important feature of fiber optic sensing is the ability to detect where an event occurred. A linear sensor potentially spanning ten, twenty, or fifty or more miles is of little use if you can’t determine where a particular event occurred. When coupled with positional information about the installed cable itself, it’s possible to derive a precise location of an event at any point along an installed cable. With the relative location known, this information can be useful for integration with various systems, such as Geographic Information Systems (GIS), Building Information Modeling (BIM), and navigation systems to provide real-time information about where something is happening.
How does it work?
The short explanation is that light transmitted through a fiber optic cable is affected by the physical environment in predictable and measurable ways. By measuring the properties of the light, it’s possible to determine both what happened and where it happened along the length of the fiber. If you want a full technical primer on the topic and more information about the individual applications and methods, the Fiber Optic Sensing Association (FOSA) has some very informative reference materials here.
A basic fiber optic sensing system consists of a length of fiber optic cable connected to an “interrogator” — effectively a computer device designed to translate the transmitted signals into useful information. An interrogator is connected to one or more fiber optic cables, effectively turning the entire length of the cable into one long sensor. For many applications, the attached cables can be dozens of miles or more in length, with current capabilities. Fiber optic cables require no power source in the field and are relatively durable and resistant to weather and temperature extremes, making fiber optic sensing an ideal solution even in the harshest of environments.
It’s particularly noteworthy that fiber optic sensing capabilities can be added to existing cable installations without a significant impact on data transmission capabilities. This makes fiber optic sensing a value-added service that both improves the value of existing fiber optic installations and provides additional incentive for new installations.
Applications in Transportation and Infrastructure
Real-Time information will make roads safer
Ask yourself the question: “What if the road can tell me what’s happening?” What if it can tell you about the disabled vehicle, traffic jam, landslide, or even the bridge in danger of collapse long before you arrive and regardless of whether there’s anyone else around to report it? What if the road can tell you where the other cars are, whether there are any hazards or obstacles in the roadway, or even simply warn of an unusual traffic pattern ahead? That’s exactly what fiber optic sensing can provide. Whether you’re in an old, beat-up pickup with your cell phone perched in the cupholder, riding in an autonomous vehicle with a real-time data stream, or on foot crossing an intersection, fiber optic sensing will make you safer.
Continuous monitoring will revolutionize roadway engineering
Transportation agencies spend significant time and resources to gather information about traffic counts and patterns, road deterioration and maintenance, inspections, and numerous other tasks. Many of these tasks can be greatly simplified through fiber optic sensing.
Almost anything that generates a sufficiently strong and unique force can feasibly be detected through fiber optic sensing. When you drive along a road, various forces and vibrations are transmitted to the road surface. A car traveling along the road transmits force to the road surface, providing information about its speed, location, and trajectory. The vibration of a smooth, freshly paved road is different than an old, worn-out, bumpy road. Anyone in the northeast can attest that there’s a unique “signature” when hitting one of our many, many potholes. Even something as simple as hitting the brakes or swerving can provide information about roadway conditions. This data stream opens a whole new world of possibilities for transportation engineering. Traffic statistics and patterns can be gathered continuously without stepping foot outside the office. Road surface conditions and maintenance requirements can be derived from baseline roughness information (vibration). Traffic lights can be managed to take into account not only traffic at a specific intersection but optimized to account for traffic flow on the entire road network. Beyond simple traffic monitoring, future implementations will likely account for pedestrians, bicyclists, and perhaps even a kid chasing a soccer ball into the roadway. With the potential to track the movement of individual vehicles, it may also enable higher resolution tolling/road usage, which can play a significant role in funding the roadways of the future.
Potential to monitor sub-surface conditions
No matter how frequently you inspect, many conditions are not typically recognized until it’s too late. Those familiar with the now-famous sinkhole in downtown Pittsburgh that swallowed a bus can attest to that. Many of the conditions that lead to these events can be detected using fiber optic sensing. In the case of sinkholes, broken water lines or other sources of running water are often the culprit. Fiber optic sensing installations can monitor for such conditions. In addition, future implementations may account for subtle changes in the shape of the pavement and other changes in sub-surface conditions, such as “listening” for the sound of hollow sub-surface areas to provide advanced warning.
In addition to monitoring for catastrophic failures like sinkholes, there is an opportunity to predict how sub-surface conditions impact normal, everyday wear and tear of the roadway. For example, the freeze-thaw cycle is a well-known cause of potholes and other roadway defects. While current models account for freeze-thaw to assist in roadway management, fiber optic sensing can provide high spatio-temporal resolution data, greatly improving the ability to predict and prevent potholes and other roadway defects. Quite simply, fiber optic sensing means safer, better-quality roads for less money.
Landslide and rockfall detection
I hate to keep picking on Pittsburgh, but the area is notorious for landslides and falling rocks. I can personally attest to this hazard, as I had a rock roughly the size of a large couch cushion careen down the hillside before slamming into my fender while driving along Sandy Creek Road in Penn Hills. While it’s not often feasible to implement measures to prevent landslides and rockfalls, we can at least take steps to predict and avoid them when they occur. In areas where such incidents are common or expected, fiber optic cable can be installed in the area of concern and monitored for changes in configuration and strain that may be indicative of a landslide. If explicit landslide monitoring applications aren’t feasible, installations in nearby roadways can often pick up on the sound, vibrations, and other phenomena indicative of a landslide. In this and other situations where a potential hazard may not be immediately known or identified, simply providing drivers and pedestrians a warning of “unusual/potentially hazardous activity detected” may be sufficient to avoid catastrophe.
Integration with AVs benefits everyone
It wouldn’t be appropriate to discuss the future of transportation without covering the role of autonomous vehicles (AVs). While AVs currently rely on built-in sensors such as Lidar, cameras, and other sensors, they are limited by their field of view — what they can “see.” With fiber optic sensing coupled with other smart road technology, it will soon be commonplace for the vehicles and roadway networks to “talk to each other.” Roadway sensor systems may provide the vehicle with information about its surroundings, such as what’s around the corner or over the hill. An appropriate installation may even warn the vehicle about whether the road surface is potentially icy or otherwise slippery. Vehicles may supplement the fiber optic systems by providing feedback, such as providing information that helps determine whether an event in the roadway is due to a pothole or a piece of lumber that fell out of the back of a truck. While AVs are getting smarter and more capable by the day, there’s only so much a given vehicle can “see” on its own. Through integration with fiber optic sensing technology, AVs can move one step closer to the goal of providing efficient transportation while eliminating traffic accidents.
Closing thoughts
With all of the potential applications, it’s safe to say that fiber optic sensing will be a key component of the future of transportation. With such promise to improve nearly every aspect of transportation, the only question that remains is, why aren’t we doing this already?
