Unintended effects: blue lights vs heroin

Many public toilets across the country have been fitted with blue lights to make it hard for heroin users to see their veins. It works… just about, but has enoughs issues to illustrate of two basic rules of design:

Rule 1: Your design probably won’t have the desired effect on the behaviour you want to change

Case in point – it didn’t take long for addicts to work out that you could just mark your veins beforehand. The blue lights also make things worse for some: 

“Blue lights make it more difficult to see superficial veins, such as those in the forearm. However, when people are injecting into deeper veins such as the femoral vein, the presence of blue lights is an ineffective deterrent. Groin injectors are not looking for a visible vein, and so can continue to inject in such bad lighting. ” 

“The provision of blue lights does not prevent or reduce injecting per se. Rather, it results in displacement of the problem from that arena to other arenas. Worse still, it is likely to mean that activity is moved from one specific location to a number of locations.”

Etc… more points here.

As Dan Lockton would say as part of his excellent Design With Intent, it’s a flawed architecture of control:

“So the blue lighting ‘works’, but is it really a good idea to increase the risk that an injection will be done wrongly – maybe multiple times? This is perhaps a similar argument to that surrounding delibrately reducing visibility at junctions: the architecture of control makes it more dangerous for the few users (and those their actions affect) who ignore or bypass the control. This seems to be an architecture of control with the potential to endanger life, although the actual stated intention behind it probably includes ’saving lives’.”

UPDATE 27 Mar 09 – Dan Lockton pointed out another flawed scheme yesterday: pink lighting to deter teenagers by highlighting their acne… 

Rule 2: Your design will probably affect behaviours you didn’t want to change at all (!) 

In economics there’s a great concept called an externality, which is when other people bear a cost (or receive a benefit) from things you did but didn’t pay (or get compensated) for. For example, when you drive your car you pollute, but don’t really take into account the full cost of the damage your exhaust fumes are causing. That cost to the environment which you don’t have to cover is the negative externality, or side effect.

Almost every design will have side effects where they affect areas which have nothing to do with the purpose of the design – a kind of design externality. The blue light is a good example of this too, spotted from an article about the town of Rugby which installed UV lighting in 2000, only to find that there were uninteded consequences:

Public toilets in Church Street, in Rugby town centre, were closed in February after a shocked cleaner discovered two people having sex inside. In a report to officers, Rugby borough council head of engineering and works David Johnson said the toilets were still suffering anti-social behaviour. 

He said: “The lighting scheme has not achieved its aim. Drug users can mark their veins before entering the building.

“The subdued lighting encourages an atmosphere conducive to sexual activity, while it is off-putting to the public wishing to use the facilities.

“Another problem is that graffiti written in certain pens looks spectacular under UV lighting.”

Now council officers have suggested many of the toilet blocks in the town centre be knocked down and rebuilt from scratch to combat the problem.

Every non-trivial design will have unintended consequences – by being aware of this you can capture them and turn them to your advantage. This is particularly important when dealing with complex social issues.

The larger the gap between the simplicity of the solution and the complexity of the problem, the larger the potential for side effects.

This makes it extra important to put yourself in the shoes of your users (no pun intended) to work out what they need and iterate until you can provide it.

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