I wonder if Spring and Autumn are worse times for cars hitting cyclists due to dazzling low sun shining on windscreens misty with plasticiser film or just moisture?
It's difficult to tell, but it looks like Spring is the worst in the UK. I threw the just-published RRCGB 2018 tables into a stats package and the rate that accidents happen seems fairly constant over most of the year but for a noticeable surge around April.
Although, if we suspect people cycle a bit less in winter, then the rate that accidents happen seeming fairly constant would mean that winter has a higher risk. As usual, we are limited by how little cycling trip data we have.
In case anyway has a copy of R (from r-project.org) to hand, here's what I was looking at. I'm a bit rusty at this language and I apologise for some of this terminology ("Accidents"!) but it's what RRCGB still uses:
Accidents <- read.csv("Accidents_2018.csv")
Casualties <- read.csv("Casualties_2018.csv")
Vehicles <- read.csv("Vehicles_2018.csv")
cycles <- subset(Vehicles, Vehicle_Type==1)
cycle_accidents <- subset(Accidents, is.element(Accident_Index, cycles$Accident_Index))
plot(sort(as.Date(cycle_accidents$Date, "%d/%m/%Y")))