Road accidents are nearly always caused by a driver's mistake or misjudgement. Sometimes they occur because of unusual road or weather conditions.
This story is about an accident which had a most unusual and alarming cause.
As a result of the accident, John, who tells the story, was given a 'breathalyser' test by the police. A motorist can be asked to take a test if the police suspect that he has drunk too much alcohol to be able to drive safely. The motorist is asked to blow into a plastic bag through a tube containing coloured crystals. The amount of alcohol in the motorist's breath is shown by the change in the colour of the crystals. If the test is positive, further tests are carried out.