We have a request for some information, we have a customer that has a Mercedes-Benz C-Class, she travels to work using the Blackwall tunnel occasionally she is getting a message on her dash board informing her that the radar sensor on her car is dirty, as this is a new car and clean we believe this message is being caused by an outside interference. We have been in contact with Mercedes-Benz in Germany and they have informed us that this can be caused by a “heavy outside radar signal”, the only time this message appears is when the vehicle is driven into the Blackwall tunnel. My request is are there any radar type sensors or transmitter on either tunnel for monitoring traffic flow that might be fitted to the tunnels which could cause interference of this type?

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Our ref: FOI-0045-1920/GH

Thank you for your request received by Transport for London (TfL) on 3 April 2019 asking for information about the Blackwall Tunnel.

Your request has been considered under the requirements of the Freedom of Information Act 2000 and our information access policy. I can confirm that we do hold some of the information you require.

There is no radar or microwave detection operating at the same frequency range installed within the Blackwall Tunnel northbound.

The only radar frequency based system installed in the Blackwall Tunnel is a radio rebroadcast transmitted into the tunnel via the Leaky Feeder antenna system located in the roof of the tunnel and running for the entire length.  The  leaky feeder is a coaxial cable with sections of the outer screening removed at regular intervals so that the radio signals can “leak” from he cable.  

The primary purpose of the system is to provide radio coverage in the event of an incident  in order to inform the general public via mobile phone coverage and radio channels.  The radio systems primary purpose is to broadcast evacuation messages in the event of an emergency. The Emergency services radio systems provides coverage to the Police, Fire Service and Ambulance Service during an incident while the maintenance radio system provides coverage for maintenance crews during closures and incidents.

The tunnel also has mobile phone coverage.  The mobile phone network is operated by Telefonica (O2) and Vodafone, but shares the same leaky feeder antenna.  The following frequencies / bands are what the system is capable of using, not what it actually may be using.  The frequencies that are in use at any time are controlled by the mobile operator. 

EGSM900:      925-960MHz/880-915MHz

GSM1800:     1805.1-1810.9MHz/1710.1-1715.9MHz

1810.9-1816.7MHz/1715.9-1721.7MHz

1816.7-1846.7MHz/1721.7-1751.7MHz

1846.7-1876.7MHz/1751.7-1781.7MHz

UMTS:            2110-2125MHz/1920-1935MHz

2125-2135MHz/1395-1945MHz

2135-2150MHz/1945-1960MHz

2150-2160MHz/1960-1970MHz

                        2160-2170MHz/1970-1980MHz

If this is not the information you are looking for, or if you are unable to access it for some reason, please do not hesitate to contact me.

If you are not satisfied with this response please see the attached information sheet for details of your right to appeal.

Yours sincerely

Graham Hurt

FOI Case Officer

FOI Case Management Team

General Counsel

Transport for London

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