IMPLICATIONS OF THE INTERRELATION OF INVESTMENTS AND MAINTENANCE

CONDITIONS OF OPERATIONS IN VARIOUS TRANSPORT FIRMS VARY WIDELY; THE FIRMS WHICH HAVE THE LOWEST TOTAL MAINTENANCE AND INVESTMENT COSTS FOR A GIVEN LEVEL OF SERVICE HAVE HAD RELATIVELY HIGH CAPITAL COSTS FOR A LOW MAINTENANCE COST PERCENTAGE. IN SUCH FIRMS, THE TIME DURING WHICH VEHICLES WERE IMMOBILIZED FOR MAINTENANCE WAS VERY SHORT. ALL FIRMS OF THIS TYPE HAD TWO THINGS IN COMMON: THE LIFETIME OF VEHICLES WAS RELATIVELY SHORT, 9 TO 10 YEARS APPROXIMATELY, AND THERE WAS A TENDENCY TO AVOID OVERHAULS OR IMPORTANT REPLACEMENTS, THUS NEEDING VERY LITTLE MAINTENANCE LABOUR PER VEHICLE. THERE EXISTS AN OPTIMUM LIFETIME FOR EACH OPERATIONAL SITUATION, WHICH DETERMINES THE RIGHT BALANCE BETWEEN MAINTENANCE COSTS AND INVESTMENT COSTS. ALTHOUGH THESE CONCLUSIONS WERE DRAWN FOR BUSES, THEY CAN EQUALLY BE APPLIED TO RAILWAY ROLLING STOCK AND OTHER TRANSPORT VEHICLES; IT SHOULD BE POINTED OUT THAT THE OPTIMUM LIFETIME OF BUSES IS SHORTER THAN THAT OF RAILWAY ROLLING STOCK.