The following is taken from an email circular put out by the Office of the Traffic Commissioner:
The government will be testing its new Emergency Alerts in East Suffolk on 25 May between 1pm and 2pm.
What Emergency Alerts are
Emergency Alerts are messages sent to mobile phones within an area of risk. They don’t need your location or phone number. The service will be used to warn you about life-threatening emergencies such as severe flooding or terror attacks.
Only the government and the emergency services can send them. All compatible mobile phones will be able to receive them. If you don’t have a mobile, you’ll still be kept informed through other channels.
If you are working in the area during this time
If you are working within the area on Tuesday 25 May between 1pm and 2pm, you will receive this Emergency Alert test. It will make a loud siren-like sound and show a message on your phone screen.
If you receive a test alert, you do not need to do anything.
What should I or my drivers do if I receive the Emergency Alert message while driving?
You should not read or otherwise respond to an Emergency Alert whilst driving.
It is illegal to hold a mobile phone while driving.
You must have hands-free access such as voice command, a dashboard holder or mat, or a windscreen mount and the device must not block the driver’s view of the road or the traffic.
The Emergency Alert will appear on your device for 20 seconds and you will hear a loud siren-like sound for up to 10 seconds.
You should continue to drive and not respond to the noise or attempt to pick up the mobile phone and deal with the message.
Find somewhere safe and legal to stop before reading the message.
Learn more about Emergency Alerts and look out for the nationwide information campaign.