Full marks to dieseldave for answering both parts of the question correctly, although I must also acknowledge mushroomman’s correct answer to part 1 of the question in identifying it as the A55.
It is, indeed, the A55 in Caernarvonshire (as it was then) between Penmaenmawr and Llanfairfechan. This stretch of road is known as Pen-y-Clip Viaduct which was opened in October 1935 by Minister of Transport, Hore Belisha ( also of beacon fame), the new road, viaduct and tunnels took 5 years to build at a cost of a quarter of a million pounds and was at that time claimed to be the Costliest Road in Great Britain.
Since 1993, when a new tunnel was opened to accommodate the westbound route, the 1935 Pen-y-clip route has only been used in the main by eastbound traffic.
Here’s an aerial view of Pen-y-Clip still under construction, (taken from an opposite aspect to the photo above in the question), the old road can be seen running above the newer 1935 route with the main Chester - Holyhead railway passing below, note the rock-fall shelter protecting the railway tunnel portal:-

Below is another early view looking eastwards towards Penmaenmawr with the Penmaenbach tunnel portal just about visible as a small black dot in the far distance:-

Quite a feat of Civil Engineering! - Thanks to everyone who took part.
**Footnote to jimboy124:- Re your last posting and I quote:- "So i got the road number wrong !
You tell me its not CONWY !! and you spell it wrong.
And then you point out your rules for you answer in RED!
Then the next bloke you say it is CONWAY .
He is corrrect ■■
Am i being stupid ?
So it was not the A5 i was bloody close !! "
Yes sorry, to be somewhat pedantic jim, but I did ask for exact answers and I can again confirm that both parts of your answer were incorrect i.e. :- it’s not the A5 (which at it’s closest point, is approx 9 miles further west of Pen-y-Clip) and also it’s not at Conway either, (which is about 6 miles further east of Pen-y-Clip). As to the spelling, I opted to use the correct English spelling of Conway, rather than the equally correct Welsh language version.
I said that mushroomman’s answer was partly correct, he answered A55 (which is correct for part 1) and then answered Conway bypass (which is incorrect for part 2). Incidentally Conway and it’s infamous bottleneck wasn’t bypassed until the early 90’s when the A55 tunnel route under the town was opened.
The question was written in red to identify and highlight that there are, in fact, 2 parts to it and that I was asking for exact answers. No offence intended.
Hope this helps clarify things. Thanks for your participation . 