The BBC reported a rather disturbing study on safety and bicycle helmets. Drivers in the UK apparently will give far less space to cyclists wearing protective gear and reflective clothing than they do to cyclists wearing street clothes.
The offered explanation is that drivers may think the properly attired cyclist may be more experienced riding in traffic and thus ride more predictably, meaning they don’t need to give that cyclist a wide berth. Which amounts to zilch when you need to swerve to avoid debris or glass or a pothole.
That’s why cyclists have a right to the full lane in California and other states.