The most controversial upgrade of the A303 has been improvement to the road through the Stonehenge World Heritage Site, where it remains a congested single carriageway road.

From Workington and Cockermouth down to Calderbridge, OS Explorer map 303 shows the western edge of the Lake District National Park.PREMIUM FINE ART PRINT - luxury heavywight 310gsm, 100% cotton rag, lightly textured fine art paper, matte finish, suitable for framing or mounting.

The road was also mentioned in the Levellers' song " Battle of the Beanfield", about the attack by police on travellers celebrating the Solstice at Stonehenge (1 June 1985): "Down the '303 at the end of the road, Flashing lights, exclusion zones". In 2016, Devon County Council announced they would self-fund improvements to the A303 between Ilminster and Honiton, which was not included in Highways England's list. Conflicts were repeated for several years in the 1980s; in 1988 a van overturned on the A303 after leaving a clash with police at Stonehenge, killing one passenger and injuring ten others.The switches between the latter to the former act as bottlenecks and are major sources of congestion along the route.