Tech in Plain Sight: Shopping Cart Locks
Have you ever noticed how expensive shopping carts are? The prices range up to $300, which might seem like a lot for something that's meant to be used for just a few hours or days. However, these carts need to be durable and last for decades, making them a significant investment for stores. But what happens when they're not returned after use? Cart theft is a major issue, with estimates suggesting that it costs hundreds of millions of dollars worldwide each year.
One solution that has been around since 1968 was patented by Elmer Isaacks. His system used magnets to prevent carts from being stolen. A cart leaving the store had a brake that would be armed by running over a magnet. Customers were expected to follow a path surrounded by magnets to prevent the brake from engaging. If you left the track, a rod passing through the wheel locked it. However, this system has several problems, including the need for multiple magnets and the risk of someone figuring out how the system works and bypassing the brakes.
But there are also low-tech ways to stop cart theft. For example, some stores have barriers that are too narrow for carts to pass through, effectively trapping them inside the store. Others require a small deposit to be paid when using a cart, with the deposit being returned when the cart is returned. This not only discourages theft but also saves stores money on hiring kids to round up stray carts.
However, these low-tech solutions have their limitations. The deposit amount can be too small to deter determined thieves. And what about those who try to steal high-value carts? In recent years, more modern systems have emerged that use a perimeter fence – usually wire or magnets – to prevent carts from being rolled over it and triggering the brake.
But even these modern systems have their vulnerabilities. If someone is smart enough, they can lift one of the wheel locks and bypass the virtual fence. This means that two-wheel locks are often used, but even with these precautions, determined thieves might still find a way to get away with it.
Smart cart locks also have the potential to solve another problem: "pushout." This refers to people filling up a cart and walking out without paying. A properly equipped cart can detect if someone is trying to push out without going through a checkout line, but this technology has its limitations and is not foolproof.
Some common carts use 7.8 kHz signals on the sensing wire, which makes them vulnerable to hacking. For example, a DEFCON presentation shows how to use your phone to lock and unlock shopping carts. While this might sound like an exciting hack, it's not something that should be attempted in real life.
Despite these challenges, there are still some concerns about the security of modern shopping cart systems. If the brake locks up while you're moving quickly, it can be frustrating. And what about when you need to navigate tight spaces? The locking wheels might make it difficult to maneuver.
If you find yourself obsessed with shopping carts, there's a museum exhibit dedicated to them at the National Museum of American History. Who knew that something as mundane as a shopping cart could conceal high-tech electronics? If you're interested in learning more about this topic, it might be worth checking out their collection.