The Pacer series were built with low construction and running costs in mind, and so all of the Pacer units use:
A lightweight modified bus body and other bus components, such as seating, with a reinforced driver's cab area to comply with crashworthiness standards.

A long-wheelbase four-wheel freight-wagon-inspired underframe, rather than the conventional arrangement of two four-wheeled bogies.
This arrangement has been criticised for rough-riding, and causing loud noise and excessive wear to the wheels and track on tight curves.
The Pacer series were built with low construction and running costs in mind, and so all of the Pacer units use:
A lightweight modified bus body and other bus components, such as seating, with a reinforced driver's cab area to comply with crashworthiness standards.
A long-wheelbase four-wheel freight-wagon-inspired underframe, rather than the conventional arrangement of two four-wheeled bogies. This arrangement has been criticised for rough-riding, and causing loud noise and excessive wear to the wheels and track on tight curves.
Pacer (British Rail)