How good intentions can have unintended bad consequences

A story told through Don Norman’s eyes.

The prequel

A couple of years ago the city of Milano saw a revolution: public bikes. A good thing.

Public bikes parking

They needed places to park these public bikes, so they stole places from the private bikes parkings.

Private bikes parking

Predictable consequences

Now people with private bikes can’t find their old parkings easily. So they park their bikes wherever they find an affordance:

Wild private bikes parkings

The sequel

Some objects afford a safe parking.

Safe bike parking

While others don’t.

Unsafe bike parking

Because you can easily lift the locked bike and steal it.

Lift and steal

These two last objects are also an anti-affordance: they prevent cars to park on the sidewalk. They’ve been put where the sidewalk has a gentle descent.

Anti-affordance for cars

They were needed because the descent is an accidental signifier to crafty drivers. It communicates: you can climb the sidewalk here.

The sidewalk descent was made to afford ‘descending’ to wheelchairs, they were not made to afford ‘ascending’ to cars.

Sidewalk descent

The unintended consequences

For people in a wheelchair sometimes a problem arises unexpectedly when the wrong object (the safe pipe) is used for a noble aim (preventing cars to climb the sidewalk) and an unexpected event occurs (no more private bikes parkings around): bikes become an anti-affordance for wheelchairs.

Wheelchairs accidental anti-affordance

How do you prevent this from happening? I see two possible solutions: we could only use the unsafe pipe or create more private bikes parking around.