Trunk A-road

A4 traffic and collisions

The A4 is a trunk A-road of 135.1 miles, from City of London to City of Bristol. This page covers its traffic at 135 DfT count points since 2000 and the collisions police recorded on it.

Last updated: 15 September 2026
Data source: Department for Transport
Records analysed: 135 count points in 2025
Methodology: View methodology

Traffic in 2025 997m vehicle miles
Average daily traffic 20,208 vehicles a day, both directions
Busiest section 99,003 A4 to A316 roundabout
HGV share 3.3% of vehicle miles
Traffic since 2019 −6.6% same count points
Collisions, 2021 to 2025 2,597 54.1 per 100m vehicle miles

How busy is the A4?

On an average day in 2025, 20,208 vehicles passed each point on the A4, counting both directions. The busiest section is A4 to A316 roundabout (Hammersmith and Fulham, Hounslow), with 99,003 a day; the quietest listed is Manor Park to A346, with 5,040.

Busiest sections, 2025

A4 to A316 roundabout carries 4.9 times the road’s average flow.

Sections of the A4 with the highest average daily flow, 2025
Section	Vehicles a day
A4 to A316 roundabout Hammersmith and Fulham, Hounslow · 1.2 mi · HGVs 2.7%	99,003
A316 to M4 Hounslow · 1.2 mi · HGVs 4.3%	92,751
A3220 to A219 Kensington and Chelsea, Hammersmith and Fulham · 0.8 mi · HGVs 2.4%	79,418
A3002 to A310 Hounslow · 0.7 mi · HGVs 2.9%	48,994
St James St to Hyde Park Corner Westminster · 0.6 mi · HGVs 2.3%	46,143
Earl's Court Rd to Thurloe Place Kensington and Chelsea · 1.1 mi · HGVs 2.0%	43,891
M4 jn2 to A406 Hounslow · 0.7 mi · HGVs 3.1%	43,800
M4 J2 to A3002 Hounslow · 0.9 mi · HGVs 2.0%	41,705
Burghfield Rd to M4 Reading, West Berkshire · 2.2 mi · HGVs 2.3%	41,678
A3063 to A3006 Hounslow · 0.9 mi · HGVs 2.8%	39,338

Source:DfT,UK Motoring analysis 2000 to 2025 Updated 15 Sept 2026

Route

City of London to City of Bristol · 135.1 miles

Schematic route: each line joins the junctions at the ends of a DfT count point link.

A4 traffic and collisions by section

112 sections between junctions, in route order. Each is the average of its DfT count points, weighted by length. 11 short link roads and spurs (2.0 miles) count in the road’s totals but are not listed.

Show all 112 sections Tap a column heading to sort

Sections of the A4 in route order, 2025 traffic
#
1	High Holborn to AldwychCity of London, Westminster	0.5	9,846	1.9%	–	30	340.3
2	A4200 Kingsway to Near St Clement Danes ChurchWestminster	0.1	18,131	2.3%	–	9	–
3	A301/A4200 to A301Westminster	0.2	24,960	3.3%	–	38	–
4	A301 to Northumberland AveWestminster	0.4	12,432	3.5%	−31.8%	61	–
5	Haymarket to Trafalgar SquareWestminster	0.2	8,534	7.3%	–	65	–
6	Cockspur St to Waterloo PlWestminster	0.1	18,177	2.6%	−10.7%	9	–
7	Waterloo Pl to PiccadillyWestminster	0.5	15,704	3.2%	−12.3%	46	322.1
8	St James St to Hyde Park CornerWestminster	0.6	46,143	2.3%	+3.1%	138	310.6
9	Hyde Park Corner to A315/A3216Westminster	0.4	48,003	2.0%	+5.5%	84	–
10	A315/A3216 to A308Kensington and Chelsea	0.6	26,839	2.5%	+10.4%	76	270.9
11	A308 to A3218Kensington and Chelsea	0.1	38,709	3.4%	−13.7%	9	–
12	Earl's Court Rd to Thurloe PlaceKensington and Chelsea	1.1	43,891	2.0%	−24.6%	84	93.0
13	At A3220Kensington and Chelsea	0.4	56,976	1.8%	−12.1%	12	–
14	A3220 to A219Kensington and Chelsea, Hammersmith and Fulham	0.8	79,418	2.4%	−7.6%	56	51.0
15	A219 to A306Hammersmith and Fulham	0.4	71,490	3.1%	−4.7%	10	–
16	A4 to A316 roundaboutHammersmith and Fulham, Hounslow	1.2	99,003	2.7%	−13.1%	50	22.7
17	A316 to M4Hounslow	1.2	92,751	4.3%	−4.2%	63	33.2
18	M4 to A205Hounslow	0.3	8,718	4.8%	−22.3%	7	–
19	M4 jn2 to A406Hounslow	0.7	43,800	3.1%	−3.4%	46	81.2
20	M4 J2 to A3002Hounslow	0.9	41,705	2.0%	+4.3%	61	87.7
21	A3002 to A310Hounslow	0.7	48,994	2.9%	−16.4%	33	51.9
22	A310 to A3005Hounslow	1.6	38,346	1.9%	−3.7%	71	72.6
23	A3005 Heston Rd to A3005 Jersey RdHounslow	0.1	39,654	2.8%	−13.0%	9	–
24	A3005 to A3063Hounslow	0.4	40,961	2.7%	−20.2%	11	–
25	A3063 to A3006Hounslow	0.9	39,338	2.8%	−4.4%	53	84.4
26	A3006 to A30(T)Hounslow	0.1	56,464	2.0%	−0.6%	18	–
27	A30 to A312Hounslow	0.5	30,733	3.4%	−16.5%	42	145.5
28	A312 to A437Hounslow, Hillingdon	1.3	18,561	2.0%	−5.7%	75	173.3
29	A437 to A408Hillingdon	0.7	16,023	2.3%	−14.9%	32	156.2
30	M4 spur road to A3044Hillingdon	1.2	17,098	4.5%	−24.1%	21	54.7
31	At A3044Hillingdon	0.7	24,102	5.6%	−14.0%	13	42.2
32	A3044 to Sutton Lane, ColnbrookHillingdon, Slough	2.1	16,492	10.6%	–	25	108.8
33	Sutton Lane to M4Slough	0.5	17,417	11.9%	−27.0%	19	123.8
34	M4 to A412Slough	2.2	16,411	2.3%	−2.1%	56	89.5
35	A412 to A332Slough	0.6	22,175	2.0%	−19.5%	36	148.4
36	A332 to A355Slough	0.8	30,613	1.7%	−9.4%	48	107.5
37	A355 to M4Slough	2.0	10,535	2.0%	−32.2%	66	144.0
38	M4 to Hitcham RdSlough, Buckinghamshire	0.8	14,982	1.7%	+14.7%	18	98.6
39	Hitcham Rd, Slough to A4094Buckinghamshire, Windsor and Maidenhead	1.3	24,641	1.8%	+2.5%	15	26.9
40	A4094 Ray Mead Road to A4/A308 RoundaboutWindsor and Maidenhead	1.2	26,125	1.2%	–	23	50.8
41	A4/A308 Roundabout to A404(M) J9Windsor and Maidenhead	2.0	23,021	0.8%	–	13	20.1
42	A404(M) J9 to A404(M) Junction 9Windsor and Maidenhead	2.8	13,460	4.2%	−28.0%	11	16.6
43	A404(M) Junction 9 to A3032Wokingham	1.7	18,141	1.6%	−22.3%	9	–
44	A3032 to A321Wokingham	1.1	15,489	2.3%	−6.2%	8	–
45	A321 to B478Wokingham	1.2	19,401	1.5%	−15.9%	11	24.7
46	B478 to Pound Lane, SonningWokingham	0.8	18,223	2.2%	−2.4%	7	–
47	Pound Lane, Sonning to B3350 Pitts Lane roundaboutWokingham	1.0	18,262	1.9%	−2.7%	11	34.9
48	B3350 Pitts Lane roundabout to A3290Wokingham	1.0	19,193	3.6%	−14.5%	13	36.8
49	A3290 to A329Wokingham, Reading	0.6	25,527	3.0%	+6.3%	27	101.8
50	A329 to A327EReading	0.8	11,817	1.7%	−6.8%	36	214.3
51	A327E to A327WReading	0.1	11,142	2.1%	+2.8%	fewer than 3	–
52	A327 to A33Reading	0.4	6,790	0.6%	−5.7%	7	–
53	A33 to A4155Reading	0.7	13,524	0.9%	−16.7%	27	149.6
54	A4155 to Honey End LaneReading	1.0	19,640	3.1%	−8.7%	26	74.0
55	Honey End Lane to Burghfield RdReading	0.2	21,552	2.9%	+32.3%	5	–
56	Burghfield Rd to M4Reading, West Berkshire	2.2	41,678	2.3%	+4.2%	23	14.7
57	M4 to Waterside Drive, ThealeWest Berkshire	0.4	36,161	5.9%	−1.1%	fewer than 3	–
58	Waterside Drive, Theale to A340West Berkshire	1.1	32,577	5.9%	−1.1%	19	31.7
59	At A340West Berkshire	2.7	22,684	5.8%	−7.9%	17	15.3
60	A340 to Pipers Way, ThatchamWest Berkshire	4.7	15,762	6.0%	+7.4%	24	19.4
61	Pipers Way, Thatcham to A339 intersectionWest Berkshire	3.7	17,468	5.5%	+5.2%	53	46.3
62	A34/A4 Roundabout to Junction A4/A339West Berkshire	1.5	14,405	1.6%	–	11	49.0
63	At A34 spurWest Berkshire	0.3	22,594	2.1%	+14.8%	0	–
64	A34 spur to A338West Berkshire	6.8	11,154	3.4%	−12.5%	16	11.7
65	At A338West Berkshire	0.2	15,850	3.3%	−3.0%	fewer than 3	–
66	A338 to B4192West Berkshire	0.2	10,797	2.8%	−1.8%	0	–
67	B4192 to Manor ParkWest Berkshire, Wiltshire	2.7	6,238	4.2%	−6.2%	6	–
68	Manor Park to A346Wiltshire	6.8	5,040	4.0%	−43.8%	10	16.6
69	A346 to Barn StreetWiltshire	0.2	19,175	5.1%	−8.1%	fewer than 3	–
70	A435 to A436Wiltshire	0.5	12,745	3.0%	−0.6%	11	100.9
71	A4361 to A345Wiltshire	6.4	7,241	5.9%	−5.8%	24	29.5
72	Stockley Lane, Calne to A361Wiltshire	5.4	5,418	2.7%	−9.1%	12	22.9
73	Stockley Lane to A3102Wiltshire	0.7	12,346	2.3%	−5.1%	9	–
74	At A3102Wiltshire	0.8	18,691	1.9%	+2.9%	6	–
75	A3102 to A342Wiltshire	2.4	13,061	2.8%	+2.9%	19	34.6
76	A342 to Pewsham WayWiltshire	1.2	21,415	2.0%	+4.0%	10	23.7
77	Pewsham Way to A420 roundaboutWiltshire	2.5	26,078	2.1%	+0.9%	13	11.7
78	A420 to A350Wiltshire	0.8	18,127	1.4%	−15.8%	14	54.6
79	A350 to B4528Wiltshire	0.3	17,177	2.0%	−6.2%	6	–
80	B4528 roundabout to A350Wiltshire	0.5	20,020	1.3%	−1.6%	4	–
81	A350 to Cross Keys LaneWiltshire	1.7	20,933	1.3%	+11.0%	16	26.0
82	Cross Keys Rd to B3109 mid-junctionWiltshire	1.1	16,016	1.8%	−3.3%	10	32.1
83	B3109 mid-junction to Hedgesparrow LaneWiltshire	1.5	9,400	1.2%	−4.6%	5	–
84	Hedgesparrow Lane, Box Hill to A365Wiltshire	1.2	9,640	2.3%	−5.5%	10	48.9
85	A365 to A363Wiltshire, Bath and North East Somerset	2.8	10,771	2.2%	+0.8%	13	26.1
86	A363 to A46Bath and North East Somerset	1.7	25,646	2.0%	+7.2%	fewer than 3	–
87	A46 to A36Bath and North East Somerset	1.3	20,714	1.4%	−1.2%	11	24.0
88	A36 to A3039Bath and North East Somerset	0.1	17,172	1.5%	−5.2%	fewer than 3	–
89	A3039 to Broad StBath and North East Somerset	0.3	9,969	1.1%	−4.6%	fewer than 3	–
90	Broad St to A367Bath and North East Somerset	0.4	5,393	1.3%	−24.6%	fewer than 3	–
91	A367 to A3604Bath and North East Somerset	0.7	13,357	1.1%	−6.1%	8	–
92	A3604 to A431Bath and North East Somerset	0.2	20,590	1.1%	−5.9%	3	–
93	Bristol Road to Newbridge HillBath and North East Somerset	1.4	8,680	1.6%	–	8	–
94	A36 to A39Bath and North East Somerset	0.9	25,612	2.2%	−5.6%	3	–
95	A39 to B3116Bath and North East Somerset	3.2	23,972	4.7%	+2.3%	14	10.4
96	B3116 to A4174/A4175Bath and North East Somerset	1.9	27,307	4.3%	−0.7%	15	16.4
97	A4174 to Emery RdBath and North East Somerset, City of Bristol	1.1	36,470	1.9%	+3.9%	28	40.7
98	Emery Rd to A4174City of Bristol	0.4	36,835	1.9%	+3.9%	12	–
99	A4174 to Water LaneCity of Bristol	0.4	27,146	2.4%	+3.1%	13	–
100	A4 Eagle Road to A4 Bristol HillCity of Bristol	0.2	14,230	2.9%	−5.5%	5	–
101	Eagle Rd to A4320City of Bristol	0.6	23,702	2.5%	−7.6%	17	59.9
102	A4320 to A37City of Bristol	0.9	19,704	3.0%	−14.4%	15	46.9
103	A37 to A370City of Bristol	0.4	29,480	3.8%	−18.3%	11	–
104	A370City of Bristol	0.1	38,289	2.2%	–	24	–
105	Merchants Rd to A38/A4108City of Bristol	1.0	12,341	3.1%	−19.6%	27	118.9
106	A3029 to A4 splitCity of Bristol	0.2	12,868	1.7%	−34.2%	fewer than 3	–
107	A4176 Bridge Valley road to A3029 Brunel WayCity of Bristol	0.9	37,653	4.1%	+6.6%	4	–
108	A4176 to A4162City of Bristol	2.5	23,885	5.2%	−0.3%	21	21.1
109	A4162 to A403City of Bristol	2.1	23,019	6.1%	−1.2%	17	20.2
110	Portway roundabout to End of HE-managed section (north of bus stops)City of Bristol	0.2	22,404	8.4%	+2.3%	4	–
111	At M5City of Bristol	0.5	13,041	7.9%	+18.6%	5	–
112	M5 to A403City of Bristol	0.4	17,595	27.1%	−6.5%	11	–

Vehicles a day is the average daily flow in 2025. “Since 2019” compares the same count points. Collisions are those with the A4 as the first road, placed on the nearest section by their recorded position; rates (per 100 million vehicle miles) are shown for sections of half a mile or more with 10 or more.

A4 traffic by vehicle type

Cars and taxis make up 78.9% of the vehicle miles on the A4. HGVs account for 3.3%, rising to 11.9% on Sutton Lane to M4.

Vehicle mix, 2025

Share of vehicle miles on the A4 by vehicle type
Category	Share
Cars and taxis	78.9%
Vans (LGVs)	14.9%
HGVs	3.3%
Motorcycles	1.8%
Buses and coaches	1.2%

Source:DfT,UK Motoring analysis 2000 to 2025 Updated 15 Sept 2026

HGV share of traffic

HGVs as a share of vehicle miles on the A4, by year
Year	HGV share
2000	4.4%
2001	3.9%
2002	3.9%
2003	3.9%
2004	4.0%
2005	3.9%
2006	3.8%
2007	4.0%
2008	3.7%
2009	3.5%
2010	3.6%
2011	3.6%
2012	3.8%
2013	3.7%
2014	3.6%
2015	3.7%
2016	3.7%
2017	3.5%
2018	3.5%
2019	3.5%
2020	4.2%
2021	4.1%
2022	4.0%
2023	3.8%
2024	3.5%
2025	3.3%

Source:DfT,UK Motoring analysis 2000 to 2025 Updated 15 Sept 2026

A4 traffic trend

Traffic on the A4 came to 997 million vehicle miles in 2025. At the count points present in both years, it is down 6.6% on 2019, before the pandemic, and down 6.9% on 2015.

Vehicle miles a year

Like for like, traffic is down 13.4% on 2000.

Vehicle miles on the A4 each year, the whole road as it was that year
Year	Vehicle miles
2000	1.1bn
2001	1.1bn
2002	1.1bn
2003	1.1bn
2004	1.1bn
2005	1.1bn
2006	1.1bn
2007	1.1bn
2008	1.1bn
2009	1.1bn
2010	1.0bn
2011	1.0bn
2012	998m
2013	1.0bn
2014	1.0bn
2015	1.0bn
2016	1.0bn
2017	1.0bn
2018	1.1bn
2019	1.1bn
2020	803m
2021	884m
2022	960m
2023	974m
2024	986m
2025	997m

Source:DfT,UK Motoring analysis 2000 to 2025 Updated 15 Sept 2026

Average daily flow

Average daily flow along the A4, weighted by link length, by year
Year	Vehicles a day
2000	23,302
2001	23,501
2002	23,104
2003	23,083
2004	23,370
2005	22,786
2006	23,289
2007	22,949
2008	22,406
2009	22,205
2010	21,468
2011	21,410
2012	20,906
2013	21,190
2014	21,369
2015	21,599
2016	21,690
2017	21,732
2018	21,820
2019	21,731
2020	16,269
2021	17,914
2022	19,455
2023	19,758
2024	19,997
2025	20,208

Source:DfT,UK Motoring analysis 2000 to 2025 Updated 15 Sept 2026

The chart counts the whole road as it was each year, so new or renumbered stretches move it. The percentage changes compare only count points present in both years. In 2025, 29 of the 135 count points were counted; DfT estimated the rest from earlier counts and local trends.

A4 collisions

Police recorded 2,597 collisions with the A4 as the first road from 2021 to 2025, 562 of them fatal or serious, including 34 fatal. That is 54.1 per 100 million vehicle miles, higher than the 31.5 for all A-roads in Great Britain. On average there were 3.8 a year for each mile of road.

Reported collisions by year

Up 6.4% from 2021 to 2025.

Source:DfT STATS19,UK Motoring analysis 2021 to 2025 Updated 15 Sept 2026

Sections with the highest collision rates

Per 100 million vehicle miles, 2021 to 2025. Sections of half a mile or more with 10 or more collisions.

Collisions per 100 million vehicle miles by section of the A4, 2021 to 2025
Section	Per 100m vehicle miles
High Holborn to Aldwych City of London, Westminster · 30 collisions	340.3
Waterloo Pl to Piccadilly Westminster · 46 collisions	322.1
St James St to Hyde Park Corner Westminster · 138 collisions	310.6
A315/A3216 to A308 Kensington and Chelsea · 76 collisions	270.9
A329 to A327E Reading · 36 collisions	214.3
A312 to A437 Hounslow, Hillingdon · 75 collisions	173.3
A437 to A408 Hillingdon · 32 collisions	156.2
A33 to A4155 Reading · 27 collisions	149.6

Source:DfT STATS19,UK Motoring analysis 2021 to 2025 Updated 15 Sept 2026

A further 326 collisions were recorded at junctions where the A4 was the second road; they are not in the figures above. Fatal or serious uses DfT’s adjusted serious figures. How we count collisions

Council areas on the A4

In route order. Each is the highway authority DfT files the count points under.

City of London
Westminster
Kensington and Chelsea
Hammersmith and Fulham
Hounslow
Hillingdon
Slough
Buckinghamshire
Windsor and Maidenhead
Wokingham
Reading
West Berkshire
Wiltshire
Bath and North East Somerset
City of Bristol

Data sources and methodology

Datasets used on this page
Figures	Source	Period	Records	Updated
Traffic counts and vehicle mix	Road traffic statistics (AADF by count point) Department for Transport Derived statistics UK Motoring	2000 to 2025	135 count points in 2025	15 September 2026
Reported collisions	Road safety open data (STATS19) Department for Transport Derived statistics UK Motoring	2021 to 2025	2,597 reported collisions	15 September 2026

Annual average daily flow (AADF) is the average number of vehicles passing a point on a typical day of the year, both directions combined.
Vehicle miles are AADF multiplied by link length and 365, summed over every count point link on the road.
Sections join count point links between junctions, using the link lines in DfT’s major road database.
STATS19 covers personal injury collisions reported to the police. Damage-only collisions are not included, and not every injury collision is reported.
Serious and slight figures are DfT’s adjusted estimates, which allow for police forces moving to injury-based reporting.
Counts of one or two collisions below Great Britain level are shown as “fewer than 3”.

How we calculate these figures All data sources

Contains public sector information licensed under the Open Government Licence v3.0.

Police-reported collisions on the A4 by year: fatal or serious, and slight
Year	Slight	Fatal or serious
2021	402	98
2022	448	119
2023	411	113
2024	360	114
2025	414	118

How busy is the A4?

Route

A4 traffic and collisions by section

A4 traffic by vehicle type

A4 traffic trend

A4 collisions

Council areas on the A4

Roads that meet the A4

Data sources and methodology

Related statistics