Example Measurements

Sample emission measurement results are given for:
A commuting trip
A highway trip

Sample Results from On-Road On-Board Measurement of Emissions for a Selected Passenger Car During an Example Commuting Trip

The graph below depicts the distribution of four "driving modes" for a sample commuting trip. The trip is 10 miles long and lasted for approximately 24 minutes.  The average speed was 26 mph.  The trip includes approximately 20 signalized intersections.  The vehicle had to stop at 7 of these, and had to slow down but not actually stop at 7 others (the light turned green as the vehicle neared the intersection).  The vehicle cruising speed varied from approximately 20 to 30 miles per hour on downtown streets to approximately 40 to 50 miles per hour on primary arterials.

The data summarized in the figure below illustrate that vehicle accelerations account for the largest share of the total air pollutant emissions during the trip, even though acceleration occurred for only 18 percent of the total time of the trip and, coincidentally, over 18 percent of the total distance travelled.  Over half of the total nitric oxide (NO) and carbon monoxide (CO) emissions are attributable to acceleration, and approximately 40 percent of  the total hydrocarbons were associated with acceleration.  Acceleration accounted for a substantial share of fuel use.  In fact, fuel use was estimated to be equivalent to only 14 miles per gallon during acceleration, whereas it was nearly 44 miles per gallon during steady cruising.  The overall fuel economy for the trip was 31 miles per gallon.

The vehicle tested for this example had a manual transmission. The driver shifted to neutral during deceleration. Hence, fuel use and emissions for deceleration were relatively low in most cases.

These results are specific to a particular vehicle and to a particular travel route.

The data summarized in the graph below were obtained from on-board emission measurements conducted at NC State University in the Department of Civil Engineering.  The measurements were made using a portable on-board emission measurement system that measures both engine and exhaust emissions data.

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Sample Results from On-Road On-Board Measurement of Emissions for a Selected Passenger Car During Highway Driving

The graph below depicts the distribution of four "driving modes" for a sample trip on an interstate highway. The trip includes brief travel on regular surfaces streets prior to entering and after exiting an interstate highway. However, nearly all of the 26 miles driven during this trip were on the Raleigh Beltline, which has a cirumference of approximately 25 miles. The trip was based upon entering the inner loop of the Beltline at Western Blvd, traveling the entire loop, and exiting at Western Blvd after one complete circuit. Over 80 percent, by time, of the trip was based upon cruising at approximately steady speed. Approximately 6 percent of the time during the trip, the vehicle was accelerating (e.g., to enter the interstate, passing cars). Although acceleration accounts for only 4 percent of the distance traveled during the trip, and only 7 percent of the total fuel consumption, it accounts for over half of the total emissions of CO for the entire trip. Acceleration also accounts for a disproportionately large share of emissions of nitric oxide (NO) and hydrocarbons (HC). This example illustrates that overall vehicle emissions are influenced significantly by accelerations. Even though acceleration accounts for only a small part of this particular trip, it accounts for a significant portion of the total emissions. These results are specific to a particular vehicle and to a particular travel route.

The data summarized in the graph below were obtained from on-board emission measurements conducted at NC State University in the Department of Civil Engineering.  The measurements were made using a portable on-board emission measurement system that measures both engine and exhaust emissions data.

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ChartObject Chart 1
 
 
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This web page was designed by H.C. Frey
All items on this web site are Copyright (c) 1999 by H.C. Frey and NC State University
If you wish to use any materials from this web site, such as for publication or presentation, please contact Dr. H. C. Frey at frey@eos.ncsu.edu.