The nationwide test will take place on Sunday 23 April and has led to discussions with various stakeholders, including transport authorities, domestic violence charities and emergency services. The RAC has been consulted to reduce potential risks to drivers, while road safety campaigners have raised concerns about driver distraction.
Some domestic violence victims who use “lifeline” phones, which are hidden from their abusers, may also be put at risk if the siren detects their devices.
Meanwhile, the Football Association has requested that the warning not be sent during the televised FA Cup semi-final.
They added that fans are being informed and supported to avoid panic.
The warning disables users’ phones and leaves a “welcome message” until they acknowledge it by clicking an “OK” message.
It is illegal to hold and use a mobile phone while driving, and those caught doing so could be subject to a six-point penalty and a £200 fine.
AA president Edmund King welcomed the plan but expressed concern about the plan to hold the test on a Sunday with less experienced drivers who are often on the road.
He told the Telegraph: “If they have the phone in the car and there’s a strange noise, there can be a form of panic.
“Even if they have a hands-free system, the strange sound could mean they reach for the phone.
“So there is no doubt there is a threat of distraction for some drivers.”
Highway signs will also be used in the run-up to the test to warn motorists not to check or use their phones.
Ministers also approved a major publicity campaign to advise the public about the siren.
Despite the concerns, ministers believe the “minimal” risk to the public from testing the system outweighs the benefits of a scheme that could warn of emergencies such as floods, bushfires and terror attacks.
Similar systems are used in other European countries and the United States.
Lucy Hadley, head of policy at Women’s Aid, said it urged ministers to “ensure that the safety of survivors of domestic violence is at the heart of the scheme’s roll-out”.
She added: “The emergency alerts pose a risk not only because an abuser could discover a survivor’s second phone, but also because they could use this as a reason to escalate abuse.”
A government spokesman said: “Emergency alerts transform our ability to warn and inform people who are in immediate danger, allowing an urgent message to be sent to mobile phones in a specific area when there is a threat to life.
“At every stage of the process, we have worked with our emergency services, transport, charities and vulnerable groups to ensure people are aware of the service, and those who wish to opt-out can do so.”