M4 J33 Capacity Improvements

The works included reducing congestion and queuing around the southern perimeter of the junction through modifications to both the M4 westbound diverge and the A4232.

Client: SWTRA
Location: M4 Junction 33, Cardiff
Completion Date: 2015
Value: £5m
Contract: NEC Option D

It consisted of two distinct elements:

  1. The South East quadrant comprised the provision of a segregated left turn lane between the M4 Westbound diverge and the A4232 southbound.
  2. The circulatory carriageway comprised widening around the southern section of the gyratory, between the westbound diverge and the westbound merge connections.

The works involved:

  • Innovative infilling of central reserve to allow full lane capacity during the works under Traffic Management arrangements
  • Widen the gyratory on the Southern quadrant
  • Associated changes to lane white lining / signage etc.
  • Improvements to street lighting
  • Relocate existing traffic signals, communications plant including CCTV mast
  • Remove existing trees, street furniture etc
  • Excavate for and construct wider embankment incorporating reinforced earth slopes
  • Single lane diverge from existing slip road
  • New dedicated slip road adjacent to gyratory
  • Existing carriageway reconstruction for length of scheme
  • New / upgraded drainage
  • New road restraint system

Project Location