Karl Shapiro, the author, starts the poem with an image of a bell. At first, the bell seems peaceful, because of the words soft and silver, and the sibilance created by the two words. This starts the poem with a softer image, and the fact that people may be hurt is not mentioned until the fourth line, although there are clues in the text. This also represents that the horror of the car crash has not yet sunk into the author's mind, or his denial of the facts by concentrating on other things. The line ends with the repetition of the word beating. The word beating is strongly associated with the heart, and blood, and the repetition emphasizes the word, to bring it to our attention. In line 3, pulsing, and artery also bring to mind the same things. This seems to me to show that, although the author is trying to block out the tragedy, he is seeing death and blood in everything, and that the ambulance's red siren reminds him of the heart, as though the ambulance was living.
The ambulance is personified later, as well, and portrayed as a falcon swooping down with 'Wings in a heavy curve', and 'floating down'. By portraying the ambulance as a bird, we not only give it a semblance of life, but also the falcon only has such a heavy curve when it is flying very quickly. This emphasizes the fact that the ambulance is moving at top speed, as mentioned in line 4. The doors open and 'empty light' into the crowd. Light is often used as a metaphor for god, and godliness. The ambulance is a symbol of hope, and of salvation - not from sin, but from injury. However, the ambulance bell 'tolls once', as