MOTORISTS have been warned to expect delays when part of the City Bypass is shut in less than a fortnight to allow workers to carve out a tunnel for the Borders Railway.
A major two-lane diversion has been built about 200 metres east of Sheriffhall roundabout to take traffic while a 130ft-wide tunnel is excavated beneath the vital road link.
Switchover works are due to start on September 5.
The speed limit will be slashed from 70mph to 40mph on the alternate route, which will be used for at least eight months while the key stretch of bypass is closed.
The new tunnel will allow the old 35-mile Waverley route from Edinburgh to Tweedbank, near Galashiels, to be reopened. The £294 million rail link is expected to start in summer 2015.
The changeover to the diversion will take place each night from 7.30pm over three consecutive weeks in a bid to avoid causing chaos on the city’s busiest route.
Cars will be directed along Millerhill Road and Old Craighall Road at times until the diversion fully opens on September 20.
Network Rail project director Hugh Wark said: “As the temporary road alignment still has four lanes, it is anticipated that the impact on traffic will be minimal.
“A series of adverts will run in advance of the transition to notify road users of the temporary diversion.”
Dalkeith ward councillor Alex Bennett said contractors had done the right thing by commuters and residents, adding: “I’ve not had any complaints.”
A Transport Scotland spokeswoman said the organisation was content that traffic management arrangements along the temporary route were the most practical.
The spokeswoman said: “Traffic Scotland will be monitoring traffic conditions closely throughout the works to proactively advise road users of the current traffic conditions, which will be communicated through variable message signing, the Traffic Scotland website and Traffic Scotland radio.”
The temporary road will be removed once the tunnel is built.
Bonnyrigg-based firm Forth Stone has meanwhile been hired to restore the 19th century Newbattle Viaduct, known as Lothian Bridge, before the structure goes back into use for the Borders rail line.