Underdeck Gantry Systems

SCX has designed, manufactured, and installed a range of bridge access solutions across the UK and beyond

The Challenge

Bridges are inherently challenging structures to maintain with their size, function, location, and environmental conditions all providing complications for easy access.

With the surface in near-constant use and the ground underneath often inaccessible, bespoke solutions to enable inspection and maintenance are vital to maintaining sustainable long-term management of these critical structures.

The Solution

SCX Special Projects provides underdeck gantry access systems that are simple to operate, easy to maintain, and that minimise desruption to the bridge’s operation. This all comes together to deliver a better maintained structure and reduction in operating costs.

Our highly skilled, multi-disciplined technicians have designed, manufactured, installed and tested systems that are in use around the world, ranging from bogies and platforms, to inverted access trains. Our experience extends across all parts of these infrastructure projects, from the steel trolleys, to the power units, as well as optional features such as on-board lighting and cameras.

A robust, safe ride

  • Bridge access solutions from SCX come equipped with key safety systems required for manned equipment, including failsafe systems and the redundancy of key components

  • Complexity is kept to a minimum in order to simplify operation and minimise maintenance requirements

  • All bridge infrastructure is designed, tested, and maintained in accordance with local standards such as CS 450 (UK) and DIN 1076 (DE)


Powered platforms

  • Drive bogies are geared to provide four-wheel drive from a single motor, powering the two primary drive wheels on one of the side plates
  • A transfer driveshaft channels power across to the other two wheels on the second side plate. Idler bogies provide additional stability, guiding the trolley as it travels to prevent crabbing
  • Depending on needs, the power source may be on-board motors, batteries, or a dedicated power feed system


Bespoke features

  • Our design of the Avonmouth Bridge Gantry Bogies proved so effective, that a second order for a similar set of bogies was placed for the Tamar Suspension Bridge near Plymouth
  • This project was carried out with notable differences in safe working loads and finish, being galvanised instead of painted
  • Equipment from SCX is designed, manufactured, and tested to the client’s precise, defined specifications at our facilities in Sheffield


Range of modular bogies

  • Gantry system bogies typically run along the underside of an I-beam as they transport suspended loads, and must therefore be strong and inflexible
  • This is achieved through running the primary drive wheels along the top face of the bottom flange of the beam
  • Two secondary wheels sit on either side of the web in order to provide additional stability


Part of a bigger picture

  • Key to these projects is SCX’s in-house Electrical, Controls, and Instrumentation (EC&I) department
  • These complex integrated mechanical and electrical design solutions control and automate our bridge maintenance systems reliably, accurately, and safely
  • This expertise is applied to the controls, motors, cameras, and brakes, as well as other electronic system integrations that a project may require





Maintaining maintenence equipment

  • Bridges are built to last, but to achieve this, the infrastructure used to keep it safe and sturdy will need to be refreshed
  • One such example of this was the travelling access platforms and rails fitted to the underside of the Second Severn Crossing Bridge
  • With the maintenance platforms removed for refurbishment, a secondary, speedy access system for the underside of the bridge was required to allow the workers to reach each section quickly and safely
Rapid Access Train (RAT)

  • The diesel-powered RAT with a SWL capacity of 2.4 tonnes seats up to four persons with the trailer carrying their equipment
  • With a maximum speed of 1.5m/s along most of the track, the RAT is automatically restricted to 1.0m/s in pre-determined sections
  • A 1 tonne SWL chain hoist loads large items into the RAT through large front doors, lightweight items can be loaded by hand through a lateral sliding door

Let's talk more about bridge access solutions

If you need an innovative solution to deliver safe accessibility to a bridge underdeck, we can explore your challenge with you and advise on the best way forwards. With safety, reliability and performance always in mind.

Call us on +44 114 262 6199, email us at, or complete the contact form below and we'll be in touch.

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SCX Special Projects Ltd

Roman Ridge Road, Sheffield, S9 1GA, United Kingdom

t:  +44 (0)114 262 6199