Because it is a 3 lane carriage with excellent visibility and I seen a lot more dodgy roads that allow you to go at national speed limit.
That's your opinion, the committee that decided on the limit based on facts clearly disagree. Again, you clearly seem to think that you know best.
EDIT: What ffm said basically.
If course it is my opinion. I indicated that by saying "I think it is arbitrary". I don't understand why and I can't see a good reason for it ... I dont overly care to find either.
I just drive at the speed indicated.
@SCS started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
Because it is a 3 lane carriage with excellent visibility and I seen a lot more dodgy roads that allow you to go at national speed limit.