M4 J4B Thorney Interchange

Route

M4

Junction number

4B

Markerpost

27.5

Name

Thorney Interchange

Terminus

Not a terminus

Other routes

M25

Authority

National Highways

Restricted turns

Full access

Services

No services

Layout and signage

Watford (M1 Link)
Birmingham (M40 Link)
Heathrow Airport T4 & Cargo
Gatwick Airport (M23 Link)
Winchester (M3 Link)
M25 Link
  M25
(M1)
(M40)
    M25
(M3)
(M23)
  Heathrow Airport T4 & Cargo
Gatwick Airport (M23 Link)
Watford (M1 Link)
Birmingham (M40 Link)
M25 Link

Lane configuration

LanesLanesLanesLanesLanesLanes

  • Lane 1 exits and returns after the junction.
  • Lane 2 continues ahead.
  • Lane 3 continues ahead.
  • Lane 4 continues ahead.

LanesLanesLanesLanesLanesLanes

  • Lane 1 exits and returns after the junction.
  • Lane 2 continues ahead.
  • Lane 3 continues ahead.
  • Lane 4 continues ahead.

In this section

What's new

Imperfectly Odd: Batheaston Bypass

It has viaducts, a tunnel and plenty of controversy, but the amazing Batheaston Bypass doesn’t really work. What went wrong?

South London's lost motorways

Completing the story of London's epic Ringways, we've just published the Southern Radials, five more motorways that never saw the light of day.

To the north east!

Two new additions to our collection of Opening Booklets take us to Darlington and Middlesbrough.

Share this page

Have you seen...

Clear and legible

A century ago, one short memorandum issued by the Ministry of Transport laid the groundwork for a system of standardised, uniform road signs and a great deal more.

About this page

Published22 April 2017

Last updated26 April 2022