“Green” PORTAL:Adding Sustainability Performance Measures

to a Transportation Data Archive

Emissions Modeling

Outline• Objectives

• Freeway emissions factors

• Emissions models

• MOBILE 6 model

• PORTAL and model inputs

• Emissions measures

• Conclusions

Green PORTAL Project Objectives:

Motivations?

• Internationally, road transport is the largest anthropogenic source of urban air pollution.

• Beyond emissions, transportation is a heavy user of society’s time and energy resources.

Sustainability Performance Measures Using Archived ITS Data:1.Emissions Estimates2. Fuel Consumption3. Cost of Delay4. Person Mobility (PMT, PHT,

PHD)

(thispresentation)

EmissionsModeling

and Estimation

Factors Affecting Emissions

Emissions EstimationRegional

Fuel SalesAverage Speed Models

Modal Models

Method Carbon balance with fuel sales

Emissions rates tied to roadway average speed

Emissions based on individual vehicle modes of operation

Ideal ScopeMacro (regional, state, and national GHG inventories)

Meso to MacroMicro (link and segment estimates)

Advantages •Minimal data needs

•Only needs speed and travel data•Can be improved with other inputs (speed distribution)

•Captures more influences (Roadway and driver)

Disadvantages

•GHG emissions only•Low time and space resolution

•Does not capture driver and roadway effects•Approximates traffic effects

•Require extensive, detailed data (instantaneous speed and acceleration, vehicle fleet)

Average Speed Emissions ModelsModel Development Process:

Some Average Speed Model Considerations• Does not fully capture speed dynamics (though

facility-specific drive cycles can approximate)

• Using speed distributions (as opposed to simply mean speed) can increase estimates by up to 9%

• Accuracy increased with other inputs: hourly and roadway vehicle fleet, weather, facility type, fuel programs, etc.

• Accuracy relies on relevance of drive cycles and tested vehicles

• All emissions models have a significant level of uncertainty

MOBILE 6

1. Created by U.S. Environmental Protection Agency

2. This version (6) released January 2001; MOBILE models date back to 1978

3. Standard usage in North America for regulatory compliance (Clean Air Act)

4. Available free at: http://www.epa.gov/otaq/m6.htm

5. Soon to be replaced by MOVES model from EPA

(a robust average speed emissions model)

MOBILE 6.2

1. New facility-specific drive cycles recorded in modern American cities

2. Updated vehicles, emissions rates, regulatory programs, and driver behaviors

3. Fuel consumption and CO2 estimates not speed-dependent (only based on fuel and fleet data)

4. Non-specified parameters default to national averages (many county-specific data available from the EPA)

Improvements and caveats

Loop Detector Data20 s count, lane occupancy, speed from

600 detectors (1.2 mi spacing)

Incident Data140,000 since 1999

Weather DataHourly data since 2004

VMS Data19 VMS since 1999

Bus Data1 year stop level data

140,000,000 rows

PORTALportal.its.pdx.edu

Regional transportation data archive at PSU

Raw Data from PORTAL20-second count, occupancy, and speed

from ~600 inductive loop detectors on the Portland metropolitan freeway system

Loop Detector Data20 s count, lane occupancy, speed from

600 detectors (1.2 mi spacing)

Incident Data140,000 since 1999

Weather DataHourly data since 2004

VMS Data19 VMS since 1999

Bus Data1 year stop level data

140,000,000 rows

-Hourly weather data also available

-Auto/truck split estimates calculated from 20-second occupancy and speed

Performance Measure Methodology

MOBILE Model Input Parameter Summary

Input Parameter

Data Source(s)Difficulty to Obtain

General Sensitivity of Performance

Measures

Hourly VMT PORTAL Low High

Hourly Speed Distributions

PORTAL Low High

Vehicle Fleet PORTAL and Averages Med Medium – High

Inspection Programs

OR DEQ and Averages Med-High Low – Medium

Fuel Programs

US EPA and Averages Med-High Low – Medium

Weather PORTAL Low Low

Hourly CO2 EstimateI-5 MP 302.5 (1.4 mile

section)

Volatile Organic Compounds I-5 MP 302.5 (1.4 mile

section)

VOC Emissions From Congestions I-5 MP 302.5 (1.4 mile

section)

CO Emissions From Congestions I-5 MP 302.5 (1.4 mile

section)

A Quick Comparison . . .

Note: There are many other factors (temperature) and sources (non-mobile) for CO in Portland. This was simply a sample visual comparison, not a correlation analysis.

Future Improvements

Conclusion• These “green” performance measures offer key

transportation system sustainability indicators that can readily be calculated from existing PORTAL data.

• While these measures can offer new insights, they rely on the accuracy of the archived data as well as the models.

• The next step in this project will be online, automated implementation of these measures based on the methods described here.

THANK YOU!

Questions? - Comments?

Funding and support for this project is provided by the National Science Foundation, Oregon Department of Transportation, Federal Highway Administration, City of Portland, TriMet and Metro. Special thanks to the PORTAL development team, PORTAL users and the TransPort ITS committee for their feedback and support.

Thank you to Dr. Robert Bertini, Portland State University

Acknowledgments:

Photo credits: Julie Verdini and PORTAL