Almost 100 ambulance workers have been deemed unable to drive the service's new fleet of vehicles - with height and body shape listed among the reasons.
New figures have revealed that following the introduction of converted Fiat vans by the East of England Ambulance Service Trust (EEAST), 94 members were identified as being unable to drive the vehicles.
Three years ago the Trust spent £54m adding the modified Fiat Ducatos to its fleet, but has found drivers encountering a range of difficulties with them since.
The Trust has said it is working on addressing these issues, with drivers complaining of insufficient cab space in the ambulances.
It brought in specialists to assist 160 members of staff who had experienced issues with the ambulances due to their height and body shape.
From these, 94 were deemed unable to drive the vehicles, an investigation from the BBC has shown.
An EEAST spokesman said: "Our new fleet of ambulances was rolled out three years ago following extensive trials with colleagues and consultation with staff, trade unions, patients and carer groups.
“Since the rollout a small number of colleagues raised concerns about the cab area which is the same as the current national ambulance specification.
"We have been working to address these issues - which affect a small proportion of our colleagues - through assessment by an independent ergonomist to identify potential modifications to the vehicles.
"We have also retained some of our older Mercedes fleet for staff who are unable to drive the Fiat ambulances, and we are exploring further options for a more permanent solution.”
The issues with the vehicles largely affect taller members of staff, with crammed-in drivers suffering from back pains, restricted vision out of the windscreen and scraped knees and shins on dashboards.
There were also some complaints that the pedals on the vehicles were too close together for drivers in work boots to safely operate them.
The Trust has also been required to roll-out training on safely using sliding doors on the ambulances, after one member of staff got their hand trapped resulting in two broken fingers.
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