Characterization of Activity Data and Patterns of Agricultural Tractors in the San Joaquin Valley of California

The objective of this research was to collect real-world activity data from agricultural equipment that could be considered when informing air quality and incentive programs in California. This included monitoring 208 tractors via either engine hour records or data loggers, with 103 of these tractors monitored with data loggers. The results showed that the average annual hours of usage for agriculture tractors declined as a function of engine age/older engine technology. The average annual hours of usage were 60, 130, 143, 741, and 739 h, respectively, for Tier 0, Tier 1, Tier 2, Tier 3, and Tier 4 tractors. The tractors were used for about 4 h per day on average. During that time, the average engine load typically ranged between 22% and 35% for the different categories, with an overall average load percentage of 28% and an average idle percentage of around 26%. Average fuel-use rates were 4.2 gal/h, with a maximum of about 8 gal/h for the 225–478 kW category, whereas the categories <130 kW had fuel-use rates of about ≤2 gal/h. The average diesel particle filter (DPF) temperatures were ≥250°C across different power categories, although the temperature distributions showed that the DPF outlet temperature is <200°C for approximately 21.5% of the operational time, which is below the temperature typically needed for the injection of urea into the selective catalytic reduction.