Appendix B. Summary of Study Project Reported Environmental Findings

Study/Project	Results	Conclusion	Major Caveats/Limitations
Simulated Pricing Field Demonstrations
Oregon Mileage Fee Concept and Road User Fee Pilot Program	No Environmental Analysis Performed
Puget Sound Traffic Choices Study	No Environmental Analysis Performed
Commute Atlanta Mileage Based Value Pricing	No Environmental Analysis Performed
Before-After Project Evaluations – U.S.
Minnesota I-394 MnPASS HOT Lanes	Small increases and decreases in on-hour average CO levels, ranging from +0.29 to -.01 parts per million	HOT lanes had no substantial impact on air quality	None reported
	Small project-related increases in noise levels found at three sites	HOT lanes had no statistically significant change in average neighborhood sound levels	None reported
	Beneficiaries of the HOT lane included a diverse population across all income, age, race/ethnicity, employment, and mode usage groups	No significant correlation between socio-demographics and project benefits and attitudes	None reported
San Diego I-5 HOT Lanes	Estimated a.m. peak emissions on the control corridor increased three to five times more than emissions on the project corridor	The HOT lanes moderated emission levels in the project corridor	Since the impact of exogenous factors could not be precisely controlled or measured, all observed differences between the control and project corridors could not be attributed to the project.
San Diego I-5 HOT Lanes	On the study roadway, emissions increased significantly more on the HOT lanes than on the general purpose lanes	Consistent with the traffic data showing increased use of the HOT lanes
Before-After Project Evaluations – International
The Stockholm Trial	8.5 -14% decrease in emissions depending on the pollutant	The project had a positive impact on emissions	Weather conditions thought to contribute to emissions reductions to some degree
	Minor reduction in noise levels	The project did not significantly impact noise levels	None reported
	Great variation in congestion charges paid by individual Wealthy, inner-city men pay the most Higher income earners pay more than lower income earners Commercial traffic and business trips are “net winners”	How pricing revenues are redistributed is the key to total cost-benefit effects on different people	None reported
London Congestion Pricing	Emissions decreased by between 13 and 16% depending on the pollutant, for the original project Emissions decreased by between 2 and 6%, depending on the pollutant, for the Western Extension	The project had a positive impact on air quality	Roadside monitoring results inconclusive (unable to differentiate project impacts from exogenous factors) Calculated emissions did estimate project impacts
	No significant, project-attributable changes in noise levels	The project did not impact perceptible noise levels	Roadside monitoring results inconclusive (unable to differentiate project impacts from exogenous factors) Significant reductions in traffic volumes are necessary to reduce noise levels (to get the smallest discernable change in noise levels—3 dBA—traffic volumes must be cut in half)
	Actual impacts were less than travelers themselves expected Issues of greatest concern are not project related Majority of respondents found the charge affordable	No significant adverse and disproportionate impacts on environmental justice populations	Despite best efforts, some groups are likely over or under-represented in data collection Perception and attitude data are not as “scientific” as quantitative data
Singapore Area Pricing	CO reductions in a.m. peak, monthly average NOx reductions, and redeuced smoke and haze (immediately after first project)	Project had a positive impact on air quality	Declines in smoke and haze could not be fully attributed to the project
Singapore Area Pricing	Some people did not benefit from the initial project, e.g., those for whom the cost of the charge is not off-set by reduced travel time After some initial crowding, transit riders enjoyed better service as service was expanded over time Middle income travelers felt adversely effected Shifts to transit were uniform across income groups	Although not all people benefitted equally, overall, the project did not significantly and disproportionately impact lower income people	None reported