By current standards, a lock is considered “secure” if it can withstand an attack lasting 3 minutes or more by a thief using readily available hand tools. Some robust locks are sold with insurance guarantees for the bicycles they secure. Different types of locks are vulnerable to different theft-perpetrator techniques.
For maximum security, cyclists are advised to use two locks of different types. This means that a would-be thief must use two different tools to “break” the locks, thereby increasing the associated effort. Determining whether cyclists in your area use poor locks may inform intervention approaches.
The effectiveness of a lock is also dependent on the type of bike thief. Bike thieves can be divided into three categories: “joyriders,” thieves that steal for money, and those who steal by volume. Joyriders, usually people under the age of sixteen, simply take a bike because “it is there” and they want to go for a ride. Those who steal for money are often looking for a quick profit to purchase drugs or alcohol. Those who steal by volume intend to sell the bikes, often as “used” bikes, on the gray market. A lock will very easily deter the first category, which various studies have indicated make up a significant proportion of all bike thefts. A lock can also deter the second type, especially if they need cash quickly.
It is estimated that if a lock takes more than five minutes to remove, the thief will move on. Bicycle locks do little to deter organized bike crime as there have been cases where entire racks have been stolen with the bikes still attached.
Despite how strong it may be, a bicycle lock is only as effective as the structure it is attached to. A bike locked to a metal bike rack is generally safe. Since these racks usually consist of both vertical and horizontal bars, bikes cannot be easily removed. However, despite their safety, these racks are not always used. Due to space constraints, bike racks are sometimes placed far from the entrance to a destination. This scenario results in a significant drop in usage, where it has been observed that people will not use bike racks more than 150 feet (46 meters) away from an entrance. Instead, cyclists will use whatever is available and “fly park” their bikes. The most common objects used are parking meters, posts, or something similar. Unlike bike racks, these objects do not have any horizontal sections that prevent a bike from being lifted off. They are therefore much less secure.
A lock is the most important bike protection tool. However, once a bike is stolen, the only tool that can help during the theft and after is Bluetooth or GPS tracker.