The M4
The M4 carries 0.16 times the national average rate of motorcyclist killed-or-seriously-injured casualties, per mile ridden — measurably below average.
Figures for the M4
Rate
346
motorcyclist KSI per billion vehicle miles, over 0.087bn miles ridden
95% interval
234 to 495
national average 2,170
Compared with the national average
0.16x
the whole interval sits below it
Killed or seriously injured
30
2021-2025, of which 1 killed
Exposure
0.087bn
motorcycle vehicle miles ridden on this road over the five years
All casualties
Not published
all-severity total is published only for the headline tables
Count against rate
Britain's danger rankings usually count casualties, which rewards long, busy roads. The M4 is 88th by count of 1,710 ranked roads, and 1,458th by rate — below average once the 0.087 billion miles ridden on it are taken into account. See the full ranking.
The M4 on the map
The road as mapped, with the motorcycle collisions recorded on it between 2021 and 2025.
Loading map
Cyclists
Method and source
Motorcyclist casualties on this road from DfT STATS19, 2021-2025, divided by motorcycle traffic on the same road from the DfT annual average daily flow counts. KSI means killed or seriously injured. The interval is the 95% confidence interval on the rate; a rate is never shown without the miles it was divided by. We publish a page for a road only where that interval clears the national average of 2,170 KSI per billion vehicle miles, so roads that cannot be told apart from average have no page.
DfT STATS19 casualty and collision files 2021-2025, and DfT AADF traffic counts 2021-2025, both under the Open Government Licence v3.0
Contains public sector information licensed under the Open Government Licence v3.0.