The section of Tuen Mun Road where the bus plunged off was not regarded as particularly dangerous, even though 250 accidents have been recorded on the three-lane, dual highway over the past two years.
A spokesman for the Transport Department said no point along the 17km route from Tsuen Wan to Tuen Mun was classified as a black spot.
He said a site is classified as a traffic black spot when, in a 12-month period, there are nine or more accidents involving injuries, or the number of pedestrians hurt in accidents is six or more.
Figures from the Transport Department show that there were 108 accidents, including two fatal ones and 26 serious incidents, on Tuen Mun Road in the first half of this year.
In the whole of last year, 248 accidents, five of them fatal and 68 serious, were recorded. There were 250 traffic accidents, four of them fatal and 74 serious, in the year before that.
Yesterday's incident is the worst on the road since it opened to traffic in 1978.
But there have been several other serious accidents on the highway in the last 12 years: