Work on a £22m project to upgrade two stretches of major road into a dual carriageway has begun.
The plans for the A66 in County Durham and North Yorkshire are aimed at improving safety.
The two schemes are for Greta Bridge to Stephen Bank and Carkin Moor to Scotch Corner and will mean an extra 6.8 miles (11km) of dual carriageway.
Between 1992 and 2005 there were 139 accidents on these two stretches, with 22 people killed and 91 seriously hurt.
During the work, which is expected to take between 12 and 15 months to complete, new carriageways will be built alongside the existing road.