M25

M25 Junction 21: Chiswell (M1, A405)

Map of M25 Junction 21: Chiswell — M25 Junction 21: Chiswell. Map data © OpenStreetMap contributors. Map drawing © Corporate Ace Limited.

Junction 21 at Chiswell is where the M25 meets the M1, between London and the north. It is motorway-to-motorway only. Bricket Wood, Bedmond and Woodside are close by. Leavesden Country Park is about a mile and a half south-west, and Garston station about two miles south.

This is where the M1 and the M25 meet, so most drivers pass through rather than leave: hauliers, coaches, and people driving north to see family. If your route uses both, check this page and the M1's own news.

Heading north or south on the M1? Our M1 Junction 6A page ↗ (opens in a new tab) covers this same interchange from the M1 side.

Check this junction now: live M25 speed flow map · latest M25 traffic news · M25 serious incidents · M25 accidents

M25 Junction 21 Now: Accidents, Incidents and Roadworks

Live traffic news at M25 Junction 21

Incidents and roadworks between Junction 20 and Junction 22 that we are aware of.

M1 northbound Jct 6 to Jct 8 carriageway closure

PlannedRoadworksClockwise Road closed

Time now: Wednesday, 21 October 2026, 21:37 (9:37pm)

21:28 (9:28pm)21 Oct 2026reported 9 min ago

Location: link road from M25 J21 clockwise to M1 J6A northbound
Direction: Clockwise
Lanes closed: Carriageway closed
Reason: Roadworks
Schedule: 22:00 (10pm) Wed 21 Oct 2026 → 05:00 (5am) Thu 22 Oct 2026

Forecast - not confirmed

🚧HA scheduled: 22:00 (10pm) Wed 21 Oct 2026 → 05:00 (5am) Thu 22 Oct 2026 starts in about 22 minutes · lasts ~7h 00m

This is the news for Junction 21 only, not the whole M25. For the rest of the motorway see all the latest M25 traffic news, the overhead signs and the speed limits in force now.

Updated 21:37 (9:37pm) Wed 21 Oct 2026

Live Traffic Speeds at M25 Junction 21

The speed strip below shows the M25 around this junction, both directions, from National Highways’ live data, checked every five minutes.

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60 mph +50–5930–4915–29under 15

closedM62connecting motorwayA6A road👈M1our site: tap for its map

services, on the side you can reach them

crashincidentqueueroadworksspeed limitspeed shown on the signsstop-startoverhead sign

reported by drivers, which can’t always be relied onconfirmed by National Highways

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Go to our live M25 traffic speed flow map ›

In an emergency call 999. To report a problem on a motorway, call National Highways on 0300 123 5000 (24 hours).

NOTE: The speed flow, overhead sign messages or other information shown on our live traffic speed flow map is updated every few minutes. We cross check the data and aim to provide warnings if there could be a delay or an inaccurate speed reading. There can be occasions, beyond our control, and despite our best efforts where the speed flow could be inaccurate. We cannot therefore guarantee the speed you can expect on any stretch of the motorway is always accurately shown. However we hope you will find our live traffic speed flow map a useful tool in trying to plan your journey. Safe driving.

All the latest M25 traffic news →Live M25 traffic speed flow map →

M25 J21 in Our Records

Incidents here, last 13 days10 collisions, 1 breakdown or obstruction

Typical time to clear–too few cleared incidents to say yet

Slowest daytime hour clockwise16:00–17:00average 46 mph (typical 58 mph)

Slowest daytime hour anticlockwise17:00–18:00average 41 mph (typical 53 mph)

The one incident we recorded at J21 in the last 13 days was a breakdown or obstruction. Clockwise, the slowest daytime hour is 16:00, about 12 mph below the typical speed. Anticlockwise, the slowest daytime hour is 17:00, about 13 mph below the typical speed.

Average speed by hour of day at J21

our average, last 10 daysNational Highways’ typical speed

Clockwise

Anticlockwise

Incidents per week at J21

collisionsbreakdowns and obstructions* part week: we started recording during it

The latest 1 here

Thu 15 Oct, 17:47 (5:47pm) Broken Down Vehicle ✓Reported by National Highways
M25 anti-clockwise between junctions J21 and J20
✓ Cleared after about 14 minutes

Built from our own records of National Highways’ live data for the M25 either side of J21: speeds from 10 days of five-minute readings, incidents from the last 13 days (we started recording incidents on 09/10/2026). Each incident is counted once. Updated every five minutes.

Junction M25 J21, Chiswell
Roads at this junction M1, A405
Nearest town Kings Langley, 2.9 miles west
Junction before J20, Kings Langley, about 2.8 miles in a straight line
Junction after J21A, Bricket Wood, about 0.5 miles in a straight line

Around M25 Junction 21: Chiswell: Towns and Places on the Map

Map of the area within about 5 miles of M25 Junction 21: Chiswell, showing the towns, villages, roads and places to visit — The area within about 5 miles of M25 Junction 21. Map data © OpenStreetMap contributors. Map drawing © Corporate Ace Limited.

Places on the Map Near M25 Junction 21
Place	What it is	From the junction
Woodside Stadium	Venue	About 1.5 miles south
Leavesden Country Park (South Side)	Park or nature reserve	About 1.5 miles south-west
Hanstead House	Historic house or castle	About 1.5 miles south-east
Garston	Railway station	About 2 miles south
Munden House	Historic house or castle	About 2 miles south-east
The Hypocaust	Attraction	About 2.5 miles north-east
Apsley	Railway station	About 3.5 miles west
Millennium Maze	Attraction	About 4 miles north-east