Under the name “Turbostar”, Bombardier (originally Adtranz) combined four classes of diesel multiple units that were based on the classes 165/166 “Networker Turbo”. Production took place at the Adtranz/Bombardier factory in Derby. They were the first new vehicles purchased by British railway companies after privatization, with Chiltern Railways as the first customer.

They are designed to be coupled with the “Sprinters” of classes 150 to 159. However, with a top speed of 100 mph (161 km/h), they are faster over longer distances. Compared to their predecessors, they are also largely constructed of aluminum, but have more powerful engines from MTU.

The different variants each consist of two to four cars. The first delivered Class 168 is also called “Clubman”. Classes 170 and 171 only differ in the couplers. The class 172 has bigger differences, as it has more powerful engines and a mechanical six-speed gearbox instead of the two-stage hydraulic Voith gearbox. In the subclasses 172/2 and 172/3 there are additional gangways on the fronts.