Noise and vibration were measured in the cabs of 35 locomotives from 15 locomotive series. Noise exposure was estimated from measurements of A-weighted equivalent noise levels with personal noise dose meters. For the evaluation of the frequency and fluctuation level, noise samples were recorded under different operating conditions. Of the measured equivalent noise levels, 45% exceeded 85 dB during a period of 0.5-2 h. Vibration was measured from the seat of the locomotive cab, at the foot of the seat and at floor level. The most harmful vibration was detected between 1 and 3 Hz of the 1/3 octave band, the 8 h risk limit of Finland''s Institute of Occupational Health standard 2631 often being exceeded in this range. The thermal climate in 20 locomotive cabs was evaluated under summer and winter conditions with the measurement of temperature, velocity, relative humidity of the air and globe temperature. The results were compared with the international comfort and health standards for climatic conditions. The analyses indicated nonuniform air temperature and draft in the cabs. These discomforts were caused by the cold air flow and the low surface temperature of the windows in winter. The thermal climate parameters often exceeded the comfort limit in summer. Diesel exhaust constituents were measured in the air of 4 roundhouses and of 9 cabs during a trip. Four constituents with the highest dilution coefficients were chosen for measurement, i.e., NOx acrolein, formaldehyde and total dust. The Finnish threshold limit values of these substances were not exceeded. The highest values were obtained in the sheds, where exposure times were very short. Ergonomic surveys utilizing spatial measurements, observation, photography and interviews were made for the 10 most common Finnish locomotive series to provide for recommendations for the design of new locomotive types and for the modification of those in use. The features requiring the most urgent attention were connected with climbing in and out of the cab, with the design of the seats, the controls and the instrument board. The steps were usually in an upright angle, positioned at unequal intervals and slippery; the ascent and descent were dangerous. The seats were defective in design and poorly adjustable. The seat of the locomotive assistant was unfeasible in many cabs. The arrangement of the dials on the instrument board was often confusing. Many of the controls were far from the engineer and inadequately designed.