## 3 Vehicle Replacement Optimization Model
### Environmental Profiles of Life Cycle Phases
#### 3.3.3 Maintenance and Repairs  
Maintenance and repair LCIA was calculated based on detailed service documentation of 40 Ford Focus II cars, including 20 petrol and 20 diesel vehicles. All cars were heavy duty fleet vehicles, with annual mileages over 30,000 km. The cars were regularly serviced as part of a business contract in the licensed Ford service center in Szczecin (Poland). * Preventive maintenance;
* Irregular maintenance;
* Preventive maintenance with a shorter engine oil exchange interval;
* Repair following failure;
* Accident repair. Preventive maintenance covers regular procedures according to the producer's service schedule, including exchange of liquids, filters, belts, etc. The range of service operations was the same for both fuel versions and was conducted at equal intervals, each 15,000 km. The content of parts replaced in each interval equals the average result of all cars. Irregular maintenance includes those exchange operations that are due to normal wear and tear of components, including parts that do not last the lifespan of a vehicle, such as brakes, clutch, shock absorbers, suspension, etc. However, in this option such components are replaced only when they are in limit wear condition. Because the lifespan of these components depends on the driver's behavior and road conditions (season, city, highway), the range of exchanged parts is different in different cars. Exchange intervals are also different. Data about material content during each exchange and about exchange intervals were collected for each individual car. The shorter engine oil exchange interval model is specific for diesel cars with DPF. It covers a problem discussed in Section 3.1. In this maintenance model, oil was exchanged according to indications every 4000 km. It increased the number of exchanges from 10 to approximately 37 for the car lifespan defined in the study. The model used data about the number and frequency of oil exchanges that were accompanied by the replacement of a filter, an oil screw and a carter joint. Failure repair covered those components which failed prematurely, such as alternators, turbochargers, engines, gear boxes, computer control systems, steering wheels, etc., which were expected to last the whole car use period. Breakdown notifications were analyzed separately for each fuel version. Most cases were about failure of suspension, steering and brake systems. Failure cases linked to engine, electrical and electronic systems were on the same level. Breakdown cases of the drive system were the least frequent. Material data gathered on an irregular maintenance basis were collected for each notification. This study did not cover accident repair cases. The consequences of road accidents are difficult to estimate. The environmental impact of accident repairs can only be approximated with acceptable probability based on statistical analysis of a large sample of cars. Since this kind of data is not available, the assessment of accident repair impact was conducted for three real-life scenarios differing in range and complexity. The list of replaced elements is presented in Table S2 of the Supplementary Materials. The material content of exchanged parts was determined for each scenario. LCI includes processing data of spare part production. Production requirements for each component were determined based on expert knowledge. Data of waste produced, energy and heat consumption were collected for each operation of component replacement. The average energy consumption of each operation was estimated based on monthly energy consumption in the service center, the number of man-hours at each work station and time standards for exchange procedures defined by the manufacturer. Additionally, the transport of spare parts and waste removal were also taken into account. Ultimately, all processes (component transformation, transport and energy sources) were represented by best fit data from Ecoinvent.