Eighteen minutes, usually

Text: an original contemporary consumer-report-style practice extract.

The route planner promised that I could walk from the market hall to the health centre in eighteen minutes. The number appeared beside a blue line crossing the station arcade, with no range and no explanation. I left at lunchtime and arrived twenty-two minutes later. A queue had formed at one pedestrian crossing, and shoppers filled the narrow arcade. Four extra minutes hardly ruined my day, but the exact-looking estimate had encouraged me to treat delay as an exception.

I tried the route again early the next morning. This time, shutters blocked the station arcade until eight o’clock. The planner immediately replaced its blue line with a longer route and changed the estimate to twenty-seven minutes. On a third walk, made in the middle of a quiet afternoon, the arcade was open, the crossings were clear and I reached the health centre in eighteen minutes. The original figure was possible; it was not equally dependable in every set of conditions.

The planner later began displaying the arcade’s opening hours and a usual journey time of eighteen to twenty-five minutes. That information is less tidy than a single number, but more useful to anyone deciding when to leave. A journey estimate does not need to predict every slow pedestrian or crowded pavement. It does, however, need to show enough of its assumptions for users to recognise when its precision is only temporary.

In this extract, the writer tries to show that a precise journey estimate can hide the conditions on which it depends.

Evaluate how successfully this is achieved. Support your views with detailed reference to the extract.