The Swedish furniture giant is spending £4m to improve junctions and access to a new outlet planned for Pincents Lane Retail Park in Reading.
The work includes widening Pincents Lane and replacing the existing roundabout on the A4 with a new traffic-light controlled junction.
The retailer is awaiting final agreement after plans were scaled down.
A £10m three-level store was approved in 2012 but the furniture company reduced its proposal to two storeys last year to reflect the "ever-changing retail environment".
There are not expected to be any issues over the approval of the new scheme, as a smaller store should mean fewer customers and cars travelling to the site.
Some residents and businesses had objected to the original plans because of traffic congestion fears.
Drivers are facing 40 weeks of delays as work starts ahead of the building of a new Ikea store in Berkshire.