It is a cold, clear morning, and you are inching your way along the Westlink in the company of hundreds of other bleary-eyed travellers. You are shut in by high grey walls. A van has broken down on the Clifton Street slip road, and shifting into third gear for a few precious yards feels like progress, success, release. At this hour your fellow sufferers are mostly commuters and parents on the school run. Your car is a capsule. Alone inside it you are warm and snug, insulated from the world outside by layers of metal and plastic, the familiar jangle of the radio. Everything is set up for your personal comfort and pleasure: the rake of the steering wheel, the height of the seat, the temperature of the aircon. In lines of traffic stopped in queues at slip roads and junctions there is a shared perception of personal space that has nothing to do with safe distances. Everyone is separate. You are only a matter of inches from the person in the next lane, yet you are worlds apart. You study them indirectly, covertly, for to look directly at them breaks an unspoken communal agreement. All the same, occasionally someone will stare directly at you, ripping the delicate fabric of your little world, until the line moves and normality returns. In your rear-view mirror lies another world, framed by the back window. Your vista is different, and so is your behaviour: you can make eye contact, smile, wave, gesticulate, flirt, curse. The mirror has different rules; you are not face-to-face.

This morning I’m sitting at the lights, watching as behind me a smart young blonde girl in an immaculate cream-coloured Mini fixes her makeup. It is a major junction, where the Westlink meets the M2, and she knows it will be a long time before the lights turn green. She applies red lipstick and brushes a little powder on her cheeks; the eyes have already been done. She lowers the compact and a frown of dissatisfaction scuds over her face; she cannot see the results of her efforts properly in the vanity mirror. Purposefully, she reaches over to the seat next to her, hokes momentarily in her bag, and in one perfect movement lifts her smartphone in front of her to take a picture. She turns the phone around, studies the photo and then takes another. Satisfied, she stashes the phone, pushes up the sunshade, and returns to the business of commuting. She has timed the whole operation just right. I want to blow her a cheeky kiss, to acknowledge her vanity and resourcefulness, but the lights have changed and I move off, changing quickly up into third. We will never meet.