LONDON - The police in Lincoln are using unmanned air vehicles (UAVs) to help monitor one of Europe's busiest Christmas markets. This effort aims to stop a Berlin-style terror attack. Some 260,000 people visited Lincoln Christmas market in 2016.
Four UAVs are flying over the market.
Under Civil Aviation Authority rules, UAVs are banned from flying over large crowds. An exception is made when lives are at risk.
The four UAVs cost £1,200 ($1,600) apiece and fly at a speed up to 50 mph.