Not what we'd expect:
The twentieth century is not the only time in city evolution at which traffic accidents became a concern. Around the end of nineteenth century, when all in-city transportation was hoof and foot-dependent, accidents in cities were common.
In New York, for example, 200 persons died in accidents in the year 1900, which, when transposed, means a 75 percent higher per capita rate than today. In Chicago the rate per horse-drawn vehicle in 1916 would be almost seven times the per auto rate in 1997.
This is in an environment dominated by pedestrians where traffic speeds ranged between 3 and 9mph. Indeed (in the USA) the ratio between vehicle miles travelled (VMTs) and road traffic fatalities has declined consistently since the second world war.