When Your Car Door Jams, You Use the Other Door. But What If the Only Door is INSIDE?

Interior cargo locks reduce attack surface, but they concentrate responsibility. If the lock is inaccessible, the system must detect degradation before access is needed. That’s the design problem this article addresses.

Ever had a car door lock jam on you? Frustrating—but luckily, you just shimmy around and pop open another door. Problem solved.

But in cargo trailers or containers, there’s only one door. A single point of failure. Question is: why would anyone design a lock you can’t open externally? Isn’t that asking for trouble?

Turns out, there’s a smart reason. Interior locks are actually recommended by the Transported Asset Protection Association (TAPA), a global freight security standard, because external access points become targets for thieves and accidental misuse.

In other words, external overrides aren’t just convenience, they’re vulnerabilities. You can’t really have an external override “just in case” and still claim high protection. When you design a system without an external override, reliability stops being a nice-to-have. It becomes a design obligation.

Reliability without an override

The solution is to track operation parameters continuously. The goal? Catch anomalies before they become incidents. Maintenance is scheduled proactively, not reactively, based on the tiniest deviations from normal behavior. This works well in other industries like aviation engine monitoring.

We apply the same principle to our interior locks:

• We measure how much force the actuator is using
• We track how many cycles it’s been through
• We look for changes in resistance, timing, and movement profile

Failure modes

So, what could go wrong with a lock? Locks fail quietly long before they fail completely. Failures can occur in three ways:

1. Software hiccups (like your phone freezing, annoying, but fixable)
2. Electronic glitches (think “check engine” light in your car)
3. Mechanical jams (think rusted hinge or sticky lock)

To reduce those risks, we run MTBF (Mean Time Between Failures) testing, simulate environmental wear, and apply predictive maintenance models.

But that’s not enough. Because sometimes, failure doesn’t look like failure until it’s too late.

Traditional monitoring looks for known faults. But in systems designed to run unattended for long periods, unknown degradation matters just as much. That’s why we also use anomaly detection trained on normal behavior, not to predict failure perfectly, but to flag deviation early.

How does anomaly detection work?

Imagine a security guard who doesn’t memorize faces, but learns how people normally behave. When something seems off, even if it’s never happened before—they flag it.

This technique works the same way: algorithms learn what “normal” sensor behavior looks like, then raise a red flag when something strays too far from baseline.

That’s key, because traditional systems rely on predefined fault signatures. If you’ve never seen a specific failure before, you might miss it entirely. But these algorithms say: “This pattern doesn’t feel right”—and that gives you time to act.

Think of it as keeping your car door from jamming in the first place—no awkward climbing required.

Interior locks only make sense if reliability is engineered as deliberately as security. That’s the bar we design against.

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