Meng, Yu and Debbie A. Niemeier (1998) Modeling Carbon Monoxide Concentrations as Level-of-Service D Intersections. Institute of Transportation Studies, University of California, Davis, Research Report UCD-ITS-RR-98-07
To conduct the technical analysis, a hypothetical four-leg, five-phase, pre-timed, signalized intersection was constructed with volumes and phasing designed to ensure LOS D operations. The intersection is representative, in terms of size and composition, to many intersections found in the urban areas of California with construction, management, and design oversight provided by Caltrans. The hypothetical intersection included an east-west main-line approach with three-through lanes and separated right- and left-turn lanes on the eastbound approach. The westbound main-line included three through -lanes, with one lane allotted to combined through- and right-turn volumes, and a separated left-turn lane. The side-street approaches comprised each of two through-lanes, one lane also used by right-turns, and a separated left-turn lane.
The analysis tasks undertaken to estimate modeled CO concentrations for intersections operating at LOS D included:
- 1. Estimating the highest (exceedance) and second highest (violation) modeled 8-hour CO concentrations by intersection orientation, a total of 288 runs of EPA's recommended model CAL3QHCR, for each of four worst-case meteorological conditions in California: Sacramento (1989), Redlands (1981), West Los Angeles (1981), and San Jose (1988);
- 2. Using the worst-case identified in Task 1, i.e., by location and orientation, analyzing the effects of increasing and decreasing traffic volumes and merging right- and left-turn lanes with through movements on modeled CO concentrations.
- 3. Using the worst-case identified in Task 1, i.e., by location and orientation, analyzing the effects of changing fleet characteristics on modeled CO characteristics.
The analysis results clearly demonstrate that, based on CAL3QHCR predicted CO concentrations, using worst-case meteorological conditions, employing a plethora of additional conservative inputs (e.g., pre-timed vs. actuated signalization), and assuming a 3.0 ppm background, most intersections operating at LOS D will not be likely to violate the 8-hour 9.0 ppm CO standard.