Safety schemes in the South East region
We're delivering targeted speed management changes in the South East region as part of our ongoing commitment to reduce the number of people harmed on the region’s roads.
What we're doing
Safety is and always will be our number one priority. That's why our ambition remains that no-one should be harmed while travelling or working on our roads.
Our aim is to improve road safety for all road users by introducing reduced speed limits, which we anticipate will reduce the frequency and severity of collisions.
Locations
To reduce the number of collisions at the following locations, we're proposing targeted speed limit reductions.
Our proposals are based on collision and risk assessment data.
You'll also find information here about when we're working and how this will affect you.
A1 Barnet Bypass speed limit reduction, Borehamwood to South Mimms, Hertfordshire
We’re making the A1 Barnet Bypass safer by reducing the speed limit from 70mph to 50mph.
Lower speed limits help reduce the number of road traffic collisions. This change will make journeys safer for everyone who uses this road.
The new 50mph speed limit begins on Friday 26 September 2025.
The speed limit change covers both directions of the A1 Barnet Bypass for about 3 kilometres (2 miles). This is the section between:
- Rowley Lane junction in Borehamwood
- A1(M) junction 1 / M25 junction 23 in South Mimms
Location map of speed reduction
Closures and diversions
Thursday 18 September and Friday 26 September 2025
Overnight (10pm to 6am) we’ll install the new speed limit signs and close some lanes and slip roads during this work.
Lane closures:
- lane 3 on the northbound carriageway will stay open
- lanes 1 and 2 between Rowley Lane and A1(M) junction 1 closed
Slip road closures:
- Rowley Lane slip road closed overnight
- Holmshill Lane closed overnight
- A1(M) junction 1 closed overnight
Lane and slip road diversions
If you want to join the A1 northbound. From Rowley Lane or Holmshill Lane:
- follow the diversion south to Stirling Corner junction
- then at Stirling Corner Junction join the A1 northbound
If you want to leave the A1. At Rowley Lane or A1(M) junction 1:
- continue to A1(M) junction 2
- then return southbound to reach A1(M) junction 1 / M25 junction 23 or Rowley Lane
Full closures
A1 southbound carriageway between A1(M) junction 1 and Rowley Lane closed.
Full closure diversions
For southbound traffic on the A1:
- follow signs for the M25 anticlockwise to junction 21a
- then A405 southbound
- M1 southbound to junction 4
- A41 eastbound
- and A1 northbound back to Stirling Corner junction
For non-motorway traffic:
- use the A1081 southbound
- and A411 westbound to reach Stirling Corner junction
If you need to exit at A1(M) junction 1:
- continue the A1 to Stirling Corner
- then return northbound on the A1 to reach A1(M) junction 1 / M25 junction 23.
Over the past 5 years, there have been 55 injury collisions on this section of road. The lower speed limit will help reduce collisions and make the road safer.
Speed limit enforcement
The local police are responsible for enforcing the new speed limit.
Please remember that closures can change at short notice. You can check the latest information on our daily closures page or find live travel information on our Traffic England. Our travel alerts give details of live incidents on our network.
Project information
Overview
We’re always exploring ways to make our roads safer through a better understanding of driver behaviour. We do this using collision data, risk assessments and insights.
We're proposing several speed management changes to reduce collisions.
Benefits
Safety is and will always be our number one priority.
Our ambition remains that no-one should be harmed while travelling or working on our roads.
Achieving this shared vision will benefit:
- the country as a whole
- families and individuals whose lives continue to be affected by collisions on our roads.
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