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A former control room operative at Highways England has told ITV News Meridian that staffing was 'woefully low' and that the job to monitor the road network, including smart motorways, was stressful.
The ex-employee, who did not want to be identified, said that the work load would lead to increased staff sickness, adding more pressure to the system.
"The number of staff in the room has always been woefully low.
"When additional tasks came along with smart motorways, it did anything but ease the pressure on us. Call waiting times would increase and targets of setting signs swiftly would be more challenging because you were being pulled from pillar to post.
"The job became more pressured, resulting in increased tensions, verbal conflict, long term sickness and people looked for alternative jobs.
"We needed a magic box containing replacement staff, but there wasn’t one."
Highways England say that the number of control room operatives has increased 22% since 2017 from 308 to 382.
A spokesperson said, "Our control rooms are staffed to the numbers required to safely monitor and control all our roads, including sections of motorway without a hard shoulder. We are aware of comments from a former employee and we are looking into their claims.
"We are continuing to invest in additional technology and infrastructure to further raise the bar on safety."
The questions raised by the former employee come as Transport Secretary Grant Shapps commissioned the Office of Rail and Road to carry out an independent review of safety data for the controversial schemes.
In a written statement to Parliament, Mr Shapps said: "While the evidence has suggested that ALR motorways are in most ways as safe as, or safer than, conventional ones, I am determined to go further and ensure that they are the safest roads in Britain."
Steve Gooding, director of motoring research charity the RAC Foundation, said:
"We strongly support the decision to bring in the ORR.
"Public confidence in the safety of smart motorways appears to be stuck at a low ebb and the best way to offer reassurance to sceptical drivers is by publishing comprehensive safety data that has been independently scrutinised by the regulator."
A spokesman for the ORR said "robust and trusted data and analysis is essential".
Mr Shapps published a smart motorway action plan in March 2020 with 18 measures to boost safety.
He ordered Highways England to produce a report one year on, outlining its progress and identifying actions that can be delivered ahead of schedule.<
This document will be published "by summer, once I am assured that the proposals are sufficiently robust", Mr Shapps said.
A coroner in Sheffield claimed in January that smart motorways "present an ongoing risk of future deaths" after two people were killed when a lorry driver ploughed into their vehicles while they were stationary on the M1 in South Yorkshire.
The Commons' Transport Select Committee launched an inquiry into smart motorways last month, with chairman and Tory MP Huw Merriman warning there are "genuine worries" about the roads.