The Department for Transport has not conducted studies on mobile phone coverage in tunnels.
The Heathrow Express rail service does offer uninterrupted mobile coverage in its tunnel sections. However in general rail tunnels are not equipped with GSM transceivers.
Most existing Highways Agency tunnels have Airwave transmission to support emergency services and traffic officer communications. Where provision is made for public mobile phone coverage in tunnels, suitable agreements are required with the individual mobile phone operators.
For new, longer Highways Agency road tunnels such as at Hindhead, and where tunnels are currently being upgraded such as on the A1 (M) at Hatfield, the infrastructure is being provided to support mobile phone usage. Mobile phone coverage is also available in both bores of the Dartford tunnel. For shorter tunnels generally the mobile phone signal spills through the portal enabling reception in most of the tunnel.
The management of the local road network in England is the responsibility of local highway authorities. Data on how many road tunnels on local roads in England are equipped with GSM transceivers are not held centrally.