Systems and methods for monitoring the exhaust gas composition and fine particle composition of exhaust emissions of various types of vehicles are known. For example, with regard to automobiles, it is common for emissions inspection stations (or automotive repair facilities) to utilize dynamometers for controlled engine loading tests for the purposes of exhaust emission measurement. One drawback associated with dynamometer testing, however, is that the measurements acquired often do not represent emissions under actual operating conditions when automobiles are in motion on a roadway or other driving surface.
To remedy these and other drawbacks associated with dynamometer testing, remote emissions sensing systems have been developed to remotely monitor the exhaust gas composition of automobiles traveling past “test sites” located along streets or highways. Examples of remote emissions sensing (or “cross-road”) systems are described in, for example, U.S. Pat. Nos. 5,210,702, 5,319,199, 5,401,967, 5,591,975, 5,726,450, 5,797,682, 5,831,267, and 5,877,862, each of which is hereby incorporated herein by reference in its entirety.
However, existing systems configured to remotely test emissions tend to focus on passenger cars with exhaust systems that emit exhaust relatively close to the ground. By contrast, many commercial and/or heavy-duty vehicles, such as tractor-trailers, buses, commercial trucks, and/or other vehicles, have exhaust systems that emit exhaust at a point (or points) relatively high above the ground. For example, commercial diesel vehicles may include exhaust stacks that extend up vertically from the vehicles and emit exhaust up into the air.
As should be appreciated, exhaust leaving the exhaust pipe(s) of a moving commercial and/or heavy-duty vehicle (e.g., via exhaust “stacks” of a semi-tractor) is entrained in the vehicle's turbulent wake and continues to dissipate as the vehicle travels away. Despite the present turbulence, the dissipation of the exhaust will have a directionality associated with one or both of the location at which the exhaust is emitted and/or the direction in which it is propelled by momentum upon being emitted. For example, commercial and/or heavy-duty vehicles generally emit exhaust at an elevated position and/or propel emitted exhaust either upwards or to the side. As a result, remote emissions sensing systems designed to detect emissions for low-emitting vehicles (e.g., typical passenger automobiles) may not accurately quantify the presence of components in the exhaust of commercial and/or other heavy-duty vehicles.
Conventional remote sensing systems may further produce results that may not be indicative of the emissions of a commercial or heavy-duty vehicle because, depending on the placement of the remote sensing system and/or the operation of the commercial or heavy-duty vehicle, emissions from the vehicle may be measured while the vehicle is being operated in an atypical manner. For example, the emissions may be measured while the vehicle is changing gears. Measurements taken during a brief period of atypical operation may inaccurately indicate elevated levels of emission by the vehicle.
These and other problems can reduce the benefits of remote emissions sensing systems.