From its eastern terminus between Redcar and Middlesbrough it runs past Stockton-on-Tees and Darlington mainly as two-lane dual-carriageway and single carriageway past Darlington, becoming motorway standard as the A66(M) shortly before meeting junction 57 of the A1(M). It shares the A1(M) route south to Scotch Corner, from where it continues west across the Pennines, past Brough, Appleby, Kirkby Thore, Temple Sowerby and Penrith until it reaches Junction 40 of the M6 motorway at Skirsgill Interchange, where traffic going towards Western Scotland turns onto the northbound M6. The A66 continues past Blencathra to Keswick and Cockermouth and on through the northern reaches of the Lake District before arriving at the coastal town of Workington. There is a short stretch of dual carriageway along the northern part of Bassenthwaite Lake between Keswick and Cockermouth. Whilst the eastbound section follows the straight line of the disused Cockermouth, Keswick and Penrith Railway, the westbound section has numerous bends with climbs and dips. The westbound section was closed due to flood damage in December 2015 and when it re-opened in May 2016 had been permanently reduced to a single lane. This section has a limit monitored by average speed cameras.