"As yet, the Government has issued no specific plans for turning part of the A303 by Stonehenge into a tunnel but as far as we understand, any portal would be located within the existing dual carriageway section of the road and subject to careful survey.
Work to upgrade the last remaining single carriageway section of the road is due to start in January.
The single carriageway section was included only to improve the realism of driving from the urban area onto a motorway.
The single carriageway sections A1 between Newcastle and Berwick-upon-Tweed would be converted to dual carriageway, while there are also proposals to widen the A47 in Norfolk.
The A303 is one of the most direct routes from London and the South East to Devon and Cornwall, but single carriageway sections, including around Stonehenge, suffer from bottlenecks.
Two further dual carriageway sections, from Harvey to Myalup, and around Glen Iris, opened on 17 June 1996.
Finally, after the Rijeka Zagreb motorway was completed in 2008, the works on the remaining single-carriageway section of the route intensified.
Table 1, a-c, provides examples of estimating efficiency indices for selected treatment types such as: (a) upgrading a single-carriageway to a dual-carriageway road section, (b) barrier installation - building a rigid median, on a single-carriageway road section, (c) resurfacing and replacing lenses by LEDs, at a signalized junction.
In particular, upgrading a single-carriageway to a dual-carriageway road section, building a roundabout and traffic lights' installation at a junction, were associated with considerable reductions in injury accidents, thus, supporting the results of previous studies on the subject [7, 13, 10].
The upgrading a single-carriageway to a dual-carriageway road section was applied on two road sections: (1) road No 70, km 66 77, where the road-works took place in 2007 2009; (2) road No 85, km 24 25, with actual road-works in 2007 2008.
In the second example, barrier installation - building a rigid median, on a single-carriageway road section, was implemented at four road sections, each of 3 4 km in length, between 2007 and 2009.
