Yesterday was due to be Mrs Mercer’s wedding anniversary. But instead of celebrating with husband Jason, she was putting the last preparations into the protest against the removal of hard shoulders from motorways, which she believes led to his death in 2019.
Around 50 demonstrators marched to Parliament Square on Monday to demand a ban on all-lane running (ALR) motorways, which can convert the hard shoulder into a live traffic lane. They carried 38 cardboard coffins representing the official number of people killed on smart motorways between 2014 and 2019.
Mrs Mercer believes the figure is now much higher.
She said: “Yesterday was my wedding anniversary. I had wanted to do the protest on the actual anniversary, but it fell on a Sunday, which would not have worked well for the protest here.”
Jason Mercer died after ‘minor shunt’ on M1
There have been mounting concerns about such motorways after several fatal accidents involving stationary vehicles being hit from behind.
Mr Mercer, aged 44, and Alexandru Murgeanu, 22, died near Sheffield when a lorry crashed into their vehicles which had stopped on the M1 after a ‘minor shunt’ in June 2019.
Mrs Mercer said: "They keep doing review after review after review. In the meantime, people are still dying.
"There's a really strong feeling against these. We need to embarrass the Government into actually doing something.
"We don't need a raft of changes. We just need the hard shoulder back in every single instance."
After crossing Westminster Bridge, the protesters stood outside the Department of Transport with their placards for what they called a ‘static protest’.
Mrs Mercer added that her campaign is educating the public about the risks of smart motorways.
"My husband might still be alive if he'd known what a smart motorway was," she said.
She said she had received hundreds of emails expressing support for the protest.
Janet Savage, 60, joined the demonstration after getting a flat tyre on a smart motorway several months ago.
"We couldn't get off anywhere and it was the most terrifying thing in my life," she said.
Changed tyre ‘with juggernauts going past’
She said her partner had to change the tyre on the M1 with ‘juggernauts going past’.
"I don't ever want to get on one again, ever," she added.
National Highways, the Government-owned company responsible for England's motorways and major A roads, said the chance of death on smart motorways is less than any other major road.
Chief executive Nick Harris said: "Every road death is a tragic loss of life and our thoughts remain with those who have lost a loved one.
"Safety remains our top priority and our motorways are the safest type of road in the country.
"Data shows fatalities are less likely on smart motorways than on conventional ones, but we recognise concerns continue to be raised.
"We are determined to do all we can to help drivers feel safe and be safer on all our roads. We will work with drivers to make increasingly busy motorways safer for everyone who uses them."
The Commons Transport Select Committee is due to publish a report on Tuesday on the rollout and safety of smart motorways.