It is closely followed by the A30 through Devon and Cornwall and then the M1 between London and Hook Moor in a top 10 list.
And almost a quarter of the 3,000 drivers polled in the survey admit they have either fallen asleep at the wheel or needed to take a break because they felt tired on a boring road journey.
The company behind the survey, Cornhill Direct, points to research by the Loughborough University Sleep Research Centre that reveals driver sleepiness is to blame for at least 10% of road accidents.
Cornhill spokesman Mark Bishop said: ‘If a driver begins to feel drowsy, they should find a safe place to stop and if they can, have a cup of coffee. They should not start their journey again until they feel more alert.’
Top 10 most boring roads
1. M6, stretching 230 miles between Rugby and Carlisle.
2. A30 in Devon and Cornwall.
3. M1 between London and Hook Moor.
4. M25, which carries about 196,000 vehicles daily.
5. A74 ‘The Cumberland Gap’, a six-mile A road between Carlisle and Gretna.
6. M5 southbound between junctions 15 and 24.
7. A77 in Ayrshire, which has 40 speed cameras over 29 miles.
8. M4 eastbound between Slough and London.
9. A34 between Bloxwitch and Cannock.
10. A303, a single carriageway near Andover and Stonehenge.