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Case Studies & Insights

Identifying overweight vehicles to protect ancient bridge


Swarkestone Bridge is an ancient monument just under a mile long and has 17 arches (six of which have been unaltered since medieval times). It has a weight limit of 7.5 tonnes, but vehicles frequently exceed this. A lorry driver was fined in 2016 after he ignored 8 warning signs before driving a 44 tonne lorry across the bridge.

A study by The RAC Foundation found that more than 3,000 bridges in the UK are not fit to support the heaviest lorries which can weigh up to 44 tonnes.


Together with partners Clearview Intelligence, an innovative scheme was developed that could warn approaching drivers of overweight vehicles to divert before reaching the bridge. It recognises differing weight limits by vehicle classification to encourage an overall reduction in traffic speed.

Key Highlights

  • Alerts over weight vehicle drivers of 7.5 limit ahead
  • Gives drivers a highly visible LED diversionary option before reaching a bridge
  • Year round, reliable solar powered solution deployed in a location where access to mains power is not available


Vehicle Activated Hazard Warning Signs were installed to encourage weight limit compliance and change driver behaviour. Any class of vehicles exceeding the weight limit threshold are specifically targeted by ‘7.5t 210 Yards Ahead’ Warning Signs triggered by vehicle count and classification, which has been fine tuned to detect and allow buses across the bridge.

The two hazard warning sign sites have no mains power so they are both solar powered.

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