Time Series of US On-Road CO2 Emissions (IMAGE) Boston University Caption This is a time series of US on-road CO2 emissions. Urban roads accounted for 80% of total emissions growth since 1980. Rural road emissions have been declining since 2002. Credit Boston University Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.