Real-world Emissions From 40 Heavy-Duty Diesel Trucks Recruited at Tulare, CA Rest Area

In an effort to demonstrate the ability of portable, on-board emissions monitoring systems to collect data on a large number of vehicles in a short period of time, 40 heavy-duty diesel trucks were tested in 2.5 days using a portable, on-board system. The trucks were randomly recruited at a Tulare, CA rest area, and subjected to idling and opacity tests. 21 of these trucks were also tested on the road. The equipment was well received by the drivers. Average NO_x emissions were 157-188 grams per gallon of fuel during idle and 112 g/gallon during cruise. At least one case suggesting a NO_x “defeat” strategy was observed. Elevated PM emissions during deceleration, attributed to the use of engine brake, were observed on one third of the trucks. Results show that stationary idle data can be used to identify trucks with high NO_x during acceleration, but not necessarily all the trucks with high NO_x during cruise could be identified using idle measurements.