A4 Great West Road & Bath Road Traffic: Live Cameras & Guide | JamCams
Live cameras, peak hour guide, congestion hotspots and route planning tips — updated 2026-03-02.
The A4 Great West Road is the main surface road from central London to Heathrow Airport, Bath and Bristol. Running from Cromwell Road in Kensington through Hammersmith, Chiswick and Brentford, it becomes the Bath Road as it approaches Heathrow before joining the M4 motorway. The A4 is unique among London's arterials in that it carries a very high proportion of Heathrow-bound traffic — passengers, cargo workers and airport staff — alongside commuter and local traffic. Heathrow's five terminals generate enormous traffic volumes that are felt on the A4 throughout the day.
The A4's worst congestion is at the Chiswick Roundabout (A4/A316 interchange), where traffic from the M4, A316 and local Chiswick roads converges. This junction backs up from around 07:30 on weekday mornings and again from 16:30 in the evening. The Great West Road/Hammersmith section is also slow during peaks, with the Hammersmith flyover creating its own queue. Brentford and Hounslow are slower throughout the day due to the mix of local traffic and airport workers on shift patterns, giving the A4 a more sustained level of congestion than typical commuter roads.
Morning peak: 07:30–09:30 · Evening peak: 16:30–19:00
Outside these windows, the A4 typically flows much more freely. Saturdays can be busy between 11:00–15:00.
These TfL JamCam feeds cover the A4 across London. Each image updates every 5 minutes — click any camera to see the full live feed and nearby cameras.
Showing 8 of 13 A4 cameras. Browse all cameras →
Typical congestion levels on the A4 by hour. Green = free-flowing, red/orange = heavy delays.
| 00–05 | 05–07 | 07–08 | 08–09 | 09–10 | 10–12 | 12–14 | 14–16 | 16–17 | 17–18 | 18–19 | 19–21 | 21–24 | |
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| Mon–Thu | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ |
| Friday | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ |
| Saturday | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ |
| Sunday | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ | ▓ |
The A4 to Heathrow can be unpredictable — always allow at least 30 minutes more than normal driving time suggests for flight departures.
For central London to Heathrow journeys, the Piccadilly Line tube is almost always faster than the A4/M4 during peak hours.
The Chiswick junction is the critical bottleneck — departing before 07:15 or after 10:00 avoids the worst of it.
For Bath, Bristol and longer western journeys, the M4 motorway is invariably faster than the A4 surface road beyond Heathrow.
If the A4 is heavily congested, these alternatives are worth considering:
The entire A4 within Greater London is inside the ULEZ. The eastern section around Hammersmith and Kensington is near or inside the Congestion Charge Zone boundary — check at tfl.gov.uk. Non-compliant vehicles pay £12.50 per day. Check at tfl.gov.uk/ulez.
It depends on time of day. Outside peak hours, the A4/M4 is faster than the Piccadilly line. During peak hours (07:30–09:30 and 16:30–19:00), the tube is almost always faster. The Elizabeth line from Paddington is also an option, as is the Heathrow Express (fastest but most expensive). For early morning flights (pre-07:00 departures), the A4 is usually fast and quiet.
The A4 Great West Road has a 40 mph limit along most of its dual-carriageway stretch through Brentford and Hounslow. The Hammersmith and Chiswick sections have 30 mph limits. The Bath Road section near Heathrow Airport has a 40 mph limit. Average speed cameras are present on some sections. Always check posted signs.
Chiswick Roundabout is the junction where the A4, A316 Great Chertsey Road and the M4 motorway spur all converge. Traffic from the M4 meets traffic from Richmond, Kew and the South Circular (A316) as well as the A4 itself. The roundabout's capacity is exceeded during peak hours, creating queues on all approach roads simultaneously.
The A4 Bath Road near Heathrow Airport has average speed cameras covering some sections, enforcing the 40 mph limit. These cameras were introduced to reduce accidents near the airport. The cameras are active 24 hours a day. Always check posted signs as speed limits and camera coverage can change.