A421 Pinch Point Improvements, Milton Keynes

The £17m scheme tackled a serious ‘pinch point’ on the road network accessing Milton Keynes by dualling the A421 and widening roundabouts whilst maintaining and improving pedestrian and cycle access with four new underpasses.

ABM’s precast Portal Frame System was chosen to allow rapid installation and minimisation of traffic disruption during construction. Each 8.4m x 3.1m underpass was supplied in sections split in to two elements, an upper ‘n’ section sitting on a lower ‘u’ unit.

The skewed ends of the underpasses were accommodated using uniquely shaped end units.

The scheme also featured extensive use of deeply textured internal concrete faces designed to reduce the likelihood of graffiti.

All wingwalls and headwalls were formed using precast units designed to eliminate in-situ concrete from the construction.

If you’d like to arrange training for your organisation about the features and benefits of our Arch and Portal Frame systems, please visit out Training page.

Products Supplied

  • Four 8.4m x 3.1m precast underpass structures ranging from 28 to 46m in length with skewed ends
  • Associated wing/head walls and parapet beams


Balfour Beatty Construction Services Ltd


URS/ABM Bridge Systems


Milton Keynes Council