3170 5992 043-7 at Crewe Basford Hall in May 2012. ©Dan Adkins
The IOA wagon is a type of high sided wagon designed to carry ballast and spoil. They were first put into use in 2009 and all carry the distinctive Network Rail engineers yellow colour scheme. They were given the unofficial fishkind name of "Mussel". IOA wagons have a maximum load capacity of 102 tonnes and typically travel in block trains of 10 wagons or more, delivering ballast to quarries.
(Information provided via Dapol)