You do not need to be a behavioural scientist to understand this.

Most biking is done on Sundays.

For many this is their only practice on a machine that can clear the national speed limit in first gear. Mix this with relaxed car drivers digesting a large Sunday roast possibly washed down with an ale who may or may not have other distractions in the car:- spouse, kids etc the figures are inevitable. If you ride and don't take this sort of thing into account........... :-/