Engineers' concerns are often related to the safety and efficiency of TRAINS. This is reflected in the crossword solutions for the term ENGINEERS' CONCERNS, which include 'RAILS' (4 letters) and 'TRAINS' (6 letters). Rails refer to the tracks that TRAINS run on, while TRAINS are the vehicles that transport people and goods. Engineers must ensure that both rails and TRAINS are properly maintained and functioning correctly in order to ensure the safety of passengers and cargo.