Self-Driving Cars Getting Caught Unawares Of Low Bridges And Other Onerous Heights

Dr. Lance Eliot, AI Insider

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[Ed. Note: For reader’s interested in Dr. Eliot’s ongoing business analyses about the advent of self-driving cars, see his online Forbes column:]

Watch out for that low hanging bridge!

If you live in Boston, you are likely familiar with the notion of getting “storrowed” (there’s even a hashtag for it).

On Storrow Drive, there are numerous warning signs and blinking lights that forewarn you about a bridge that has only an 11-foot clearance, and yet somehow drivers ram into it anyway.

This can be somewhat explained, according to local lore, the confusion about ramming it is due to the aspect that when new students show-up for college in Boston, they often rent a vehicle that either is higher than 11 feet, or pile stuff on top of vehicles that end-up being higher than 11 feet.

Though the Bostonian bridge story gets some occasional attention, perhaps the big winner for offending low bridges goes to the 11 foot 8 inch bridge nicknamed The Can-Opener. It’s a railroad bridge located in Durham, North Carolina and more formally known as the Norfolk Southern–Gregson Street Overpass.

Believe it or not, there is a crash into that maniacal bridge at least once per month.

That’s a disturbingly high frequency.

There doesn’t seem to be a federal mandated height maximum requirement for commercial vehicles, and the states are able to set their own height maximum restrictions, which some suggest leads to these kinds of troubles.

Typically, the maximum height allowed for a commercial vehicle is around 13 ½ feet to 14 feet or so.

Most passenger cars are around 5 to 6 feet in height.

This leaves usually plenty of room to spare for getting under most bridges and overpasses.

There are some SUV’s though that push over the 6 foot size and include the rather tallish Hummer H2 which is 79 inches in height.

Fortunately, most of these top-height passenger vehicles will still by-and-large be low enough to make it under any reasonable positioned bridge or overpass.

Drivers Ignore Warning Signs

For those of you that always carefully look for the roadway warning signs about heights, I applaud you, but I’d bet that most people don’t pay attention to those signs.

If you are driving a typical passenger car, you likely never look at the height warning signs and consider them as nothing more than a billboard that can be ignored.

When you rent a truck or put stuff onto the top of your car, presumably you should have the presence of mind to suddenly become aware of height. Not everyone though thinks that way. As a result, they fall into the rut of always ignoring the warning signs about heights and get themselves into some tight pickles.

You could also nearly excuse some of the instances by the aspect that there are warning signs about heights that are at times themselves hard to spot.

Judging Heights

If you are lucky enough to spot a height warning sign and can make sense of it, presumably you would use the added awareness to judge whether your car can fit under the height stated.

I’d bet there are some instances of human drivers that aren’t exactly sure whether they’ll be able to get their vehicle to fit under the height and rather than being cautious they take a chance anyway. Some of those chances likely turn out to be a bad bet and they end-up hitting the obstruction.

Supposing though that you do realize that you are cutting it close or that you won’t fit, and so you opt to avoid going under the bridge or overpass.

This can itself present another problem, since you need to figure out an alternative path to get to wherever you are going.

AI Autonomous Cars And Heights

What does this have to do with AI self-driving driverless autonomous cars?

At the Cybernetic AI Self-Driving Car Institute, we are developing AI systems for self-driving cars. One of the so-called “edge” problems involves having the AI be able to deal with height restrictions and circumstances such as avoiding striking a low hanging bridge or overpass.

An edge problem is considered a type of problem that is not considered at the core of an overall problem and instead is at the periphery.

That being said, it is something that those developing AI for self-driving trucks must consider at the core due to the higher likelihood of a truck encountering a height related issue.

Thus, whether developed for the purposes of a car or truck, it is a feature that has value and needs to ultimately be considered “solved” in that the AI must have a means to contend with height related considerations.

If an AI self-driving car is towing something, such as a U-Haul rented storage carrier, the towed item might involve height related considerations.

Though the self-driving car itself might not have any particular height related difficulties, the items being towed might be high enough to raise up to a low hanging bridge or overpass. Since the towed item is connected to the self-driving car, it’s up to the AI to presumably be aware of what it is towing and therefore take into account changes needed in the driving task due to the towed item.

It’s not an excuse to pretend that the AI was only responsible for the self-driving car per se.

For a true level 5 self-driving car, which is considered the topmost ranking of an AI self-driving car, the assumption is that the AI can drive the car as a human would. In that sense, it would normally be an expectation that a human driving a car that’s towing something is as responsible for the actions of the car as they are of the items towed.

If the human fails to properly tie down the towed items or fails to connect them securely to the car, it’s all on the human for having not done so.

Likewise, if the human hits a bridge with the towed item, it’s the driver’s fault, whether a human driver or the AI.

Determining Heights

Let’s start with the aspect of the AI needing to know the height of the self-driving car, which would encompass the self-driving car plus anything piled on top of it, plus anything being towed by the self-driving car.

There’s no easy automatic way right now for the AI to become aware of the height aspects.

There aren’t usually sensors on an AI self-driving car that will allow it to determine its own height and nor the height of something being towed. In the future, there might be such sensors added onto AI self-driving cars. For the moment, this being an edge problem doesn’t tend to warrant the cost and effort of including such sensors onto an AI self-driving car.

If there isn’t any such sensor already built-in, how else can the AI self-driving car ascertain the height of itself and whatever it might be towing?

One means would be to ask about the height. The AI could ask a human. If there is a human that will either be occupying the AI self-driving car during the journey, or a human that is setting the AI along on a journey (but not going to riding in the self-driving car), the AI could ask about the height aspects.

You might assume that the human(s) involved would be wise enough to forewarn the AI about any height related considerations.

I’d dare say that the human(s) might assume that the AI is already somehow able to figure out the height related aspects, and so the human(s) involved might be later shocked when they find out that their clothes and furniture spilled onto the highway because the towed storage shed bashed into the ceiling of a bridge. Probably would be best to have the AI inquire prior to a journey.

Even if the AI asks about the height, it doesn’t imply necessarily that the human(s) will accurately reply.

Using V2V And V2I To Discover Heights

Another approach to potentially figuring out the height of an AI self-driving car would be for the AI to try and communicate with other AI self-driving cars around it.

Another AI self-driving car might be able to discern the height related aspects, doing so by using its sensors such as its cameras, radar, sonic, and LIDAR. This could then be relayed to the self-driving car via V2V (vehicle-to-vehicle) communications. Thus, one AI self-driving car asks another nearby one to take a look, which after inspecting the height then is reported back to the asking AI self-driving car. Kind of a buddy system.

This brings up another facet of the height related problem.

At some point, once there are lots of AI self-driving cars on the roadways, it could be that via the use of V2V that the AI systems are trying to help each other out. While on a freeway, if there’s a car stalled in the middle of the freeway, those AI self-driving cars nearest to the stalled car can convey to other self-driving cars that are coming up upon the scene to be wary of the stalled car. In a similar manner, AI self-driving cars that are coming upon a low hanging bridge or overpass can potentially forewarn other approaching AI self-driving cars about the situation.

In the case of the Storrowed in Boston, there would be AI self-driving cars that might not yet know about the low overhang and meanwhile others that do (having driven that way before).

The ones that knew about it, either due to having driven there before or upon detecting it or having been previously informed about it, could warn other AI self-driving cars that are nearby and that are headed toward the potential obstruction. The AI of the receiving self-driving cars would then need to ascertain whether the awareness about the low hanging circumstance applied to them or not.

We are also heading toward V2I, which is vehicle-to-infrastructure communication.

There will be Internet of Things (IoT) types of devices along and throughout the roadway infrastructure and they will serve to warn drivers about various roadway conditions. These warnings might include that there’s road construction up ahead, or maybe that an intersection is blocked and to avoid it, and so on. It is anticipated that road signs are likely to be augmented with IoT, thus rather than having to only be able to visually spot a road sign, the road sign will transmit an electronic signal and thus cars can be aware of what the road sign depicts (including speed limits, cautions, and of course height warnings).

GPS And Maps Not Necessarily Cure-All

You might be saying to yourself that the GPS and electronic maps ought to be letting the AI know about any height restrictions on the roadways.

Currently, GPS mappings are somewhat inconsistent in having marked or indicated the height related aspects of a driving situation. It definitely is another source of input about heights and the AI should be considering it.

Nonetheless, it is not always guaranteed to be available and the AI needs to be finding alternative ways to further figure out the height of obstructions.


In recap, the AI needs to discover the height of the self-driving car and which would include any towed items.

It needs to be aware of height related restrictions, doing so via using its own sensors to try and identify height related concerns, along with trying to spot and read height warning signs, and possibly use GPS mappings, V2V, and V2I too.

The AI should route around any height concerns, if feasible. If the AI is taken by surprise and comes upon a height problem, it needs to devise rapidly an action plan to safely maneuver to avoid the crash.

If somehow a crash nonetheless occurs, the AI would need to become aware that a hit has occurred and take further action as appropriate.

As humans, we take for granted our ability to deal with height related driving issues. It is just the daily aspects of driving a car.

Most of the time, we don’t encounter height related problems. But, we are overall generally ready for it. Some humans regrettably aren’t paying attention or at times ignore or disbelieve when they get themselves into a height driving predicament. For AI systems that control self-driving cars, we’re all going to want and expect that the AI is on the alert and able to contend with height aspects.

As you can perhaps discern, it’s a bit of a “tall order” for the AI to do so.

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Copyright © 2019 Dr. Lance B. Eliot

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Dr. Lance B. Eliot is a renowned global expert on AI, Stanford Fellow at Stanford University, was a professor at USC, headed an AI Lab, top exec at a major VC.

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