▁all ▁over ▁the ▁world . ▁For ▁instance , ▁once ▁the ▁initial ▁A PT - E ▁experimental ▁project ▁was ▁complete , ▁it ▁passed ▁to ▁the ▁mechanical ▁engineering ▁department ▁to ▁build ▁the ▁A PT - P ▁prototype . ▁In ▁time , ▁engine ers ▁would ▁be ▁second ed ▁to ▁other ▁countries ▁for ▁varying ▁periods ▁under ▁the ▁trade ▁name ▁" Trans mark ". ▁ ▁One ▁of ▁the ▁first ▁major ▁projects ▁was ▁the ▁development ▁of ▁profile d / pre - w orn ▁whe els ▁which ▁helped ▁counter ▁the ▁t endency ▁of ▁new ▁whe els ▁to ▁h unt . ▁This ▁led ▁to ▁research ▁into ▁vehicle ▁susp ensions , ▁and ▁the ▁creation ▁of ▁the ▁four - w heel ▁High ▁Speed ▁Fre ight ▁Ve h icle ▁which ▁proved ▁stable ▁at ▁up ▁to ▁ 1 4 0   m ph ▁when ▁tested ▁on ▁the ▁roll er ▁rig . ▁ ▁Other ▁work ▁involved ▁looking ▁at ▁the ▁t amp ing ▁of ▁ball ast , ▁properties ▁of ▁sub so ils , ▁and ▁rail ▁prest ress ing . ▁A ▁large ▁part ▁of ▁the ▁network ▁had ▁been ▁converted ▁to ▁continuous ▁w eld ed ▁rail ▁which , ▁during ▁a ▁hot ▁summer , ▁caused ▁many ▁problems ▁with ▁rail ▁bu ck ling . ▁Although ▁there ▁were ▁no ▁inj uries , ▁there ▁were ▁a ▁number ▁of ▁der ail ments . ▁Att ention ▁focused ▁on ▁the ▁costs ▁and ▁benefits ▁of ▁t amp ing ▁the ▁ball ast ▁over ▁the ▁sle eper ▁ends . ▁ ▁There ▁were ▁extended ▁studies ▁into ▁metal ▁fat igue , ▁and ▁pione ering ▁work ▁in ▁ul tras ound ▁crack ▁detection