top wear(wear on the top of the railhead i.e. reduction of the railhead caused by the wheel tread - result of abrasive action between the steel wheel on the steel rail)
vertical wear(wear on the top of the railhead i.e. reduction of the railhead caused by the wheel tread - result of abrasive action between the steel wheel on the steel rail)
tread wear(wear on the top of the railhead i.e. reduction of the railhead caused by the wheel tread - result of abrasive action between the steel wheel on the steel rail)
head height loss(wear on the top of the railhead i.e. reduction of the railhead caused by the wheel tread - result of abrasive action between the steel wheel on the steel rail)