A55 upgrade at Abergwyngregyn begins in autumn
Improvement work on the A55 in north Wales is due to get under way in the autumn, taking about 18 months to complete, according to officials.
Speed restrictions will be used but all carriageways will stay open during the work at Abergwyngregyn, Gwynedd.
The £25m project involves using "low noise surfacing" following complaints from residents and reducing flooding.
There will also be upgrades to access routes on to the A55 between Junctions 12 and 13, the Welsh Government said.
People in Abergwyngregyn have said vehicle noise on the A55 is exacerbated by an echo effect in the pass leading up to Aber Falls.
Pre-construction work starts later this year and construction will start in spring 2019.
It is expected to finish in late 2020.