Hertfordshire carries the M25's northern arc and the M1 and A1(M) north out of London, with the A41 and A10 alongside. The Warner Bros. Studio Tour near Watford, Knebworth's big events and Hatfield House all draw visitors by car - check the places below before you set off.
Where National Highways recorded the most unplanned incidents in the last 30 days: collisions, breakdowns, obstructions and queues. Roadworks are not counted.
1THE A405 NORTHBOUND BETWEEN JUNCTIONS WITH THE M1 AND M25near Radlettmostly queues17incidents
2THE A1(M) SOUTHBOUND BETWEEN JUNCTIONS J8 AND J7near Stevenagemostly queues16incidents
3THE M1 NORTHBOUND BETWEEN JUNCTIONS J6 AND J8near St Albansmostly queues8incidents
4THE M25 ANTI-CLOCKWISE BETWEEN JUNCTIONS J17 AND J16near Chorleywoodmostly queues7incidents
5THE M1 NORTHBOUND BETWEEN JUNCTIONS J8 AND J9near Hemel Hempsteadmostly queues7incidents
Most incidents in Hertfordshire started between 06:00 and 09:00 UK TIME (55% of them).
Main roads in Hertfordshire
Live counts inside the county. Tap a road for its own live page.
On a motorway? If you can, get onto the hard shoulder or into an emergency area, leave by the left-hand doors and wait behind the barrier. Stuck in a live lane: stay in the car with your seatbelt on and hazard lights on, and call 999.
UK Traffic Updates