The international definition of high-speed rail embraces new lines with a top speed of at least 250 km/h (155 mph) and existing lines with a top speed of around 200 km/h (124 mph).[1] As of 2011, there are four "classic" main railway lines in Britain operating at up to 201 km/h (125 mph), plus 108 km (70 mi) of purpose-built high-speed line.