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Adjusting Weekday Traffic Using CalTrans Weigh-In-Motion Traffic Counts

Adjusting Weekday Traffic Using CalTrans Weigh-In-Motion Traffic Counts. 1997 South Coast Air Basin Modeling Studies May 22, 2002. Ozone Episodes Are Decreasing. Ozone episodes becoming rare No stage 2 episodes (> 350 ppb) since 1989 Stage 1 episodes (> 20 ppb) are rare

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Adjusting Weekday Traffic Using CalTrans Weigh-In-Motion Traffic Counts

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  1. Adjusting Weekday Traffic Using CalTrans Weigh-In-Motion Traffic Counts 1997 South Coast Air Basin Modeling Studies May 22, 2002

  2. Ozone Episodes Are Decreasing • Ozone episodes becoming rare • No stage 2 episodes (> 350 ppb) since 1989 • Stage 1 episodes (> 20 ppb) are rare • Exceedances of 90 ppb standard have been reduced by 60% • Control strategy based on HC & NOx reductions

  3. Weekend Ozone Effect Summary • “The Ozone Weekend Effect In California” • Draft Staff Report • December 15, 2000 • http://arbis.arb.ca.gov/aqd/weekendeffect/WDWE1102 • WIM data used to adjust SCAG weekday activity is same as that documented in Staff Report

  4. Weekend Ozone • Rate of decrease is lower on weekends compared to weekdays at: • Azusa, Burbank, Riverside, Pico Rivera • Lake Gregory, Upland • Difference between weekday & weekend increasing

  5. Azusa Ozone Trends Tran & Larsen 4/13/2000

  6. CalTransWIM Counters • Four SCAG Counties • Los Angeles - 7 Stations • Orange - 2 Stations • Riverside - 3 Stations • San Bernardino - 3 Stations • Counts for Heavy and Non-Heavy • Averaged by county for day of week

  7. Use of WIM Counts • Starts and stables • Adjust daily SCAG activity for day of week using WIM ratios • Adjust hourly fractions to agree with WIM hourly distributions • by county or closest county (i.e. use Orange for San Diego, use L.A. for Ventura)

  8. Activity AdjustmentMonday & Friday • Volume adjusted by time periods • by county for HDV and LDV • Hourly distribution adjusted within time period to WIM patterns • No speed adjustments

  9. Activity AdjustmentSaturday & Sunday • Daily link volumes adjusted first • by county and LDV and HDV • Hourly distributions adjusted within time periods by WIM data • Link speed set to closest link SCAG speed for volume - (LDV + HDV) • a.m. , mid-day, p.m., or night time

  10. Activity Adjustment • For each county and time period : • Volume = SCAG Volume * WIM(dow)/WIM(wed) • WIM(dow) = WIM count for day of week • WIM(wed) = WIM count for Wednesday

  11. Emission Estimates • In addition to activity, emissions are also a function of : • Ambient temperature (hourly grid cell) • Relative humidity (hourly grid cell) • Speed for weekday changed for weekend days to closest weekday speed by matching link volumes

  12. Weekend Vehicle Speeds • Vehicle speed important to estimate emissions • Weekend traffic less congested for many hours • Speed vs. VMT expected to change

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