Integration of Real-Time Air Pollution Parameters into the Decision Making Process Regarding Highway Construction Work Zone Traffic Flow

The Midac Fourier Transform Infrared air monitoring system was used to measure real-time vehicular exhaust emission concentrations of carbon monoxide (CO) and hydrocarbons (HCs) during the Purdue Vehicle Emission Monitoring and Modeling Project (PVEMP) conducted in spring and summer 1997. The experiments took place on the Borman Expressway, in Gary, Indiana and on I-65, south of Lafayette, Indiana. Concurrently, two speed-readings were acquired from the passing vehicles in the vicinity of the air monitoring system using a hand-held laser gun. The speeds were integrated to determine the speeds and accelerations of the passing vehicles at the spectrometer. An 8-mm camcorder was used to videotape the passing vehicles in order to determine the vehicle types. Three vehicle types were determined: type I represented all the automobiles, type II represented all the medium-duty vehicles including light and medium duty trucks, pick-ups, and vans, and type III represented all the heavy-duty vehicles, mainly semi-trailers. Meteorological data were also recorded from the nearest surface weather stations. Overall, 16,870 vehicles were monitored, of which 8,478 were type I, 4,829 were type II, and 3,563 were type III. The flow rates in count per minute were 8.92 for type I, 5.08 for type II, 3.75 for type III, and 17.75 for the combined fleet. However, 4,413 vehicles were retained for data analysis. These included 2,848 (65%) type I vehicles and 1,565 (35%) type II vehicles. Type III vehicles were not included in the analysis because their exhaust emission concentrations were not measured. However, their counts and frequencies were determined. The analysis for the PVEMP database showed that the exhaust emission concentrations were very variable with a logarithmic distribution. On average, type I vehicles exhaust emission concentrations were 1.10% CO and 0.23% HCs while that of type II vehicles were 1.16% CO and 0.24% HCs. They were 1.12% CO and 0.23% HCs for the combined fleet. The recorded vehicle speeds varied from 34.5 mph (55.5 kph) to 83.5 mph (134.4 kph) with a mean of 56.56 mph (91.01 kph). Accelerations varied from -4.5 mph/sec (-7.4 kph/sec) to +4 mph/sec (+6.4 kph/sec) with a mean of 0.17 mph/sec (0.27 kph/sec). With a high emitter cut-point set at 4.0% CO and 0.2% HCs, 5.7% and 49.2% of the combined vehicle fleet were CO and HCs high emitters, respectively. The instantaneous values of the exhaust CO and HCs emission concentrations exhibited a nonlinear relationship with vehicle speeds and accelerations. Using the PVEMP database, a real-time modal exhaust emission concentration model was developed. The model was based on the nonlinear multivariate regression of the speed-acceleration matrix for modal-average CO and HCs exhaust emission concentrations aggregated by vehicle type. This model, the Purdue Vehicle Exhaust Emission Model, the Borman Expressway Application (PVEM-BEA), requires input of vehicle speeds and vehicle type for each passing vehicle at a given location within a short time interval.