Operation Shield is a nationwide initiative led by British Transport Police

British Transport Police

The British Transport Police is a special police force that polices those railways and light-rail systems in Great Britain for which it has entered into an agreement to provide such services...

, where security scanners are to be deployed at major railway stations with the aim of discouraging crimninal activity on the rail network.

The initial trial of the portable equipment was undertaken by BTP in the London area and has been used in a number of towns and cities such as Cardiff

Cardiff

Cardiff is the capital, largest city and most populous county of Wales and the 10th largest city in the United Kingdom. The city is Wales' chief commercial centre, the base for most national cultural and sporting institutions, the Welsh national media, and the seat of the National Assembly for...

, Glasgow

Glasgow

Glasgow is the largest city in Scotland and third most populous in the United Kingdom. The city is situated on the River Clyde in the country's west central lowlands...

, Manchester

Manchester

Manchester is a city and metropolitan borough in Greater Manchester, England. According to the Office for National Statistics, the 2010 mid-year population estimate for Manchester was 498,800. Manchester lies within one of the UK's largest metropolitan areas, the metropolitan county of Greater...

, Leeds

Leeds

Leeds is a city and metropolitan borough in West Yorkshire, England. In 2001 Leeds' main urban subdivision had a population of 443,247, while the entire city has a population of 798,800 , making it the 30th-most populous city in the European Union.Leeds is the cultural, financial and commercial...

 and Edinburgh

Edinburgh

Edinburgh is the capital city of Scotland, the second largest city in Scotland, and the eighth most populous in the United Kingdom. The City of Edinburgh Council governs one of Scotland's 32 local government council areas. The council area includes urban Edinburgh and a rural area...

.

The initiative came after the use of metal detectors at several London Underground

London Underground

The London Underground is a rapid transit system serving a large part of Greater London and some parts of Buckinghamshire, Hertfordshire and Essex in England...

 (tube) stations led to 100 arrests and the seizure of 68 knives after around 10,000 passengers were checked.

Police Resources include;

• Both uniformed and plain-clothes police officers
• sniffer dogs
  Detection dog
  A detection dog or sniffer dog is a dog that is trained to and works at using its senses to detect substances such as explosives, illegal drugs, or blood. Hunting dogs that search for game and search dogs that search for missing humans are generally not considered detection dogs...
  
  
• mobile scanners

These were deployed at stations where robbery was known to be a problem. As well as catching
those carrying weapons, officers were able to spot individuals shying away from the detectors and made a number of arrests for other offences such as possession of drugs and stolen goods. The equipment is easily moved from one location to another making it ideal to target locations with an element of surprise.

• Operation Shield is separate to the Department for Transport's high-profile security scanning trial at Paddington Station which was set up as part of the response to the July 7 bombings

7 July 2005 London bombings

The 7 July 2005 London bombings were a series of co-ordinated suicide attacks in the United Kingdom, targeting civilians using London's public transport system during the morning rush hour....

.