A55 - today a real express way !

The study of British and Irish roads - their construction, numbering, history, mapping, past and future official roads proposals and general roads musings.

There is a separate forum for Street Furniture (traffic lights, street lights, road signs etc).

Registered users get access to other forums including discussions about other forms of transport, driving, fantasy roads and wishlists, and roads quizzes.

Moderator: Site Management Team

Post Reply
fras
Member
Posts: 2876
Joined: Tue Apr 10, 2012 18:34

A55 - today a real express way !

Post by fras » Sat Nov 27, 2021 17:50

Had a tootle out today in the MB SLK, (it needs a run now and again as it's a diesel).
Went to Rhyll and used the A55, and it was all clear with little traffic, yet this was a Saturday ! Clearly the month of the year has a huge influence !!. OK, I know you all know this anyway, but it meant our ride was enjoyable, rather than tedious. On the other roads, the storm had knocked down a lot of trees, so one had to drive cautiously at all times.
On the way back I noticed how the twilight last so long at this time of year. Why is this, anybody know ?

User avatar
Was92now625
Member
Posts: 710
Joined: Fri Jan 08, 2010 00:29
Location: near A625

Re: A55 - today a real express way !

Post by Was92now625 » Sat Nov 27, 2021 21:46

fras wrote:
Sat Nov 27, 2021 17:50
On the way back I noticed how the twilight last so long at this time of year. Why is this, anybody know ?
Twilight is longest close to the solstices (June (especially - by quite a margin) and December) and shortest around early March and October. Full answer requires spherical trig but in the summer after the sun sets it is moving "under" the pole rather than straight down. Something similar in December.

At this time of year, probably a clear horizon will have more to do with it.

User avatar
wrinkly
Member
Posts: 8502
Joined: Tue Mar 04, 2008 12:17
Location: Leeds

Re: A55 - today a real express way !

Post by wrinkly » Sat Nov 27, 2021 22:51

The first PDF link on this page shows duration of twilight against date for a range of north (upper graph of each pair) and south (lower graph of each pair) latitudes. Rhyl and the A55 are about 53 deg N so between the light blue and dark green curves. Note the y axis increases downwards. The three pairs of graphs correspond to three definitions of twilight.

If you're viewing from a vehicle doing 60mph on the A55, you lengthen the twilight by about 10% if going west, or shorten it if going east.

fras
Member
Posts: 2876
Joined: Tue Apr 10, 2012 18:34

Re: A55 - today a real express way !

Post by fras » Sun Nov 28, 2021 00:08

Many thanks to our resident experts ! I suppose this is why we get such wonderful red sunsets around this time.

Post Reply