No abstract

Mileage data collected via surveys based on self-estimation, reports from garages and other sources which use estimations are rough estimates and differ greatly from the actual mileage. Vehicle mileage is a major factor in emission calculations and needs to be as accurate as possible to obtain reliable emission models. Odometer readings are collected annually at the periodic technical inspection in Croatia. Average mileage data were analyzed for vehicles up to 20 years of age in 2017. Vehicles were classified by curb weight and fuel type. Such classification proved to follow driver behavior and the intended purpose of the vehicle. For each vehicle class, the model was applied using the vehicle age and its population size as inputs for calculating average mileage. Real data shows that vehicles in Croatia considerably exceed the estimated mileage in the years following the first registration of the vehicle and that they cannot be compared to data collected in other studies based on estimations. The difference lies in the covered mileage after vehicles reach ten years of age. The outcome of this study has resulted in a model for calculating average vehicle mileage. The model is suitable for use in various analyses for Croatia or for countries with similar driving habits and economic status now and for years to come.

No abstract

The paper shows a new method for detecting emission control system malfunction during periodic technical inspection (PTI). The on-board diagnostic (OBD) test results were collected and processed during the PTI of vehicles in Croatia in 2020. The study included petrol and diesel passenger cars that passed the tailpipe test and for which an OBD test had also been performed. In 11.5% of the tested cars, at least one stored diagnostic trouble code (DTC) was found. Due to the significant number of vehicles with identified DTCs, a new and more efficient method for the detection of potentially defective vehicles has been suggested. The introduction of the OBD test mandatory for all vehicles equipped with a European on-board diagnostic (EOBD) system is proposed. In addition to the existing OBD data, it is recommended to introduce the number of DTCs as mandatory, and such data should be relevant for passing the roadworthiness test.